I forgot to include the following sentences. Thank you very much.

1) She requested that we didn't go too near the river bank. (is it possible to use the subjunctive instead of the simple past?)
2) We were requested not to go too near the river bank. She insisted on paying the bill.
3) My brother took my mobile phone apart but he couldn't fix it.
Mobile phones really took off (became popular) in the 1960s
4) The heating system went off an hour ago and it's very cold now
Many people were killed when the bomb went off.
5) The milk went off because of the heat.
The telephone company cut my phone off because I failed to pay the bill.
6) The student cut the teacher off and started to speak.
When I lived in the country I felt cut off from social life.
7) The teacher told the students off for coming late.

1) She requested that we didn't go too near the river bank. (is it possible to use the subjunctive instead of the simple past?) Yes, you should use the subjunctive. She requested that we not go too near the river bank.

2) We were asked not to go too near the river bank. She insisted on paying the bill.

3) My brother took my mobile phone apart, but he couldn't fix it.
Mobile phones really became popular in the 1960s.

4) The heating system went off an hour ago, and it's very cold now.
Many people were killed when the bomb went off.

5) The milk went off because of the heat. I'm not sure what you mean by "went off."
The telephone company cut my phone off because I failed to pay the bill. OK

6) The student cut the teacher off and started to speak. OK
When I lived in the country, I felt cut off from social life.

7) The teacher told the students off for coming late. OK

1) It is not possible to use the subjunctive mood in this sentence. The verb "requested" already expresses a polite request, so using the subjunctive mood would be redundant. However, if you want to express a hypothetical or unreal situation, you can use the subjunctive mood. For example, "She requested that we not go too near the river bank if there were crocodiles in the water."

To check if it is possible to use the subjunctive instead of the simple past, you can analyze the context and the verb used. In this case, since "requested" is already expressing a request, using the simple past ("didn't go") is sufficient.

2) Yes, it is possible to rephrase the sentence using the passive voice and avoiding the use of "insist". The sentence can be rewritten as: "We were requested not to go too near the river bank by her, and the bill was insisted on being paid by her."

To rephrase sentences, you can try using different verb constructions, such as passive voice or different verb forms, to convey the same meaning in a different way.

3) To understand the meaning of "took off" and "went off" in these sentences, you can analyze their context. In the first sentence, "Mobile phones really took off in the 1960s," the phrase "took off" is an idiomatic expression that means they became popular or started to become successful. In the second sentence, "The heating system went off an hour ago," the phrase "went off" means it stopped working or turned off.

To understand idiomatic expressions, you can consult a reliable dictionary or do a quick internet search. Additionally, paying attention to the context and the meaning conveyed by other words in the sentence can also help you figure out the intended meaning.

4) To understand the expressions "went off" and "cut off" in these sentences, you can analyze their context. In the first sentence, "The heating system went off an hour ago," the phrase "went off" means it stopped working or turned off. In the second sentence, "Many people were killed when the bomb went off," it means the bomb exploded.

To understand phrasal verbs or expressions, such as "went off" or "cut off," you can consult a reliable dictionary or do a quick internet search. Understanding the context of the sentence can also help you grasp the intended meaning.

5) In the first sentence, "The milk went off because of the heat", the phrase "went off" means that the milk spoiled or turned bad due to being left in the heat. In the second sentence, "The telephone company cut my phone off because I failed to pay the bill," it means that the phone service was terminated or disconnected due to non-payment.

To understand phrasal verbs or idiomatic expressions like "went off" or "cut off," you can consult a reliable dictionary or do a quick internet search. Understanding the context and the meaning conveyed by other words in the sentence can also help you figure out the intended meaning.

6) In the first sentence, "The student cut the teacher off and started to speak," it means that the student interrupted the teacher and began speaking. In the second sentence, "When I lived in the country, I felt cut off from social life," it means that the person felt isolated or disconnected from social activities.

To understand the meaning of idiomatic expressions like "cut off," you can consult a reliable dictionary or do a quick internet search. Looking at the context of the sentence and analyzing the meaning conveyed by other words can also help you grasp the intended meaning.

7) In the sentence, "The teacher told the students off for coming late," it means that the teacher scolded or reprimanded the students for their tardiness.

To understand the meaning of idiomatic expressions like "told off," you can consult a reliable dictionary or do a quick internet search. Analyzing the context of the sentence and the meaning conveyed by other words can also help you figure out the intended meaning.