Could you please check these sentences I'm not sure of? Thank you.

1)Who (amont you) gets the best marks in both English and science? Who achieves the best results in both English and science? We are going to choose high achievers who get the best/highest marks in both English and science.
2) All tests much be handed up to me (or "handed in") by ten o'clock.
Which is your strongest subject?
Who is best at English?
3) Cars pollute the environment because of the gas coming out (which verb is appropriate??) of the exhaust pipes.
4) When I go to the supermarket, I usually go to the counter of sliced meats and salami first (is the word correct?). Then I go to the one of frozen food.
5) Finally, I go to the check-out counter. I show the clerk the gift card to have points credited and be eligible for prizes (I don't know how to express it)I have points credited on my gift card.
6) Learn all the verbs included in the irregular verb list in your course book pp. 206-207. Do all exercises Unit 3 from p. 120 to p. 127 (or pp. 120-127)
Study carefully the vocabulary on food on the photocopy.

1) Who among you gets the best marks in both English and science? Who achieves the best results<~~This needs to be clarified: "the best results" in doing what? in both English and science? We are going to choose high achievers who get the highest marks in both English and science.

2) All tests must be handed in to me by ten o'clock.
Which is your strongest subject?
Who is best at English?

3) Cars pollute the environment because of the gas coming out of the exhaust pipes.
Error! Gasoline doesn't come out of the exhaust pipes! The exhaust that is emitted is a combination of pollutants, depending on the type and age of the engine, but it's definitely not gasoline!
http://www.abd.org.uk/exhausts.htm


4) When I go to the supermarket, I usually go to the deli section first. Then I go to the frozen food section.

5) Finally, I go to the check-out counter. I show the clerk the gift card to have points credited and be eligible for prizes through my account.

6) Learn all the verbs included in the irregular verb list in your course book on pp. 206-207. Do all exercises in Unit 3 from pp. 120-127. Carefully study the vocabulary for food on the photocopy.

1) The sentences you provided are grammatically correct, but there are a few suggestions to improve the clarity and structure of the sentences:

- Instead of "Who achieves the best results in both English and science?", you can use "Who achieves the highest marks/results in both English and science?"

- Instead of "We are going to choose high achievers who get the best/highest marks in both English and science.", you can rephrase it as "We will select students who consistently achieve the highest marks in both English and science."

2) "All tests must be handed in to me by ten o'clock."

- Both "handed up" and "handed in" are correct, but "handed in" is the more commonly used phrase.

- To answer the second question, you can simply say the subject you excel in the most. For example, "My strongest subject is mathematics."

- To answer the question "Who is best at English?" you can simply say the name of the person who is the best at English. For example, "John is the best at English."

3) "Cars pollute the environment because of the gas emitted from the exhaust pipes."

- The appropriate verb to use in the sentence is "emitted" as it accurately describes the action of gases being released from the exhaust pipes.

4) The word "salami" is correct. The sentence structure is clear, but you can improve the flow by using the word "firstly" or "first" before "Then I go to the one of frozen food." For example, "Firstly, I go to the counter of sliced meats and salami. Then I go to the one for frozen foods."

5) "Finally, I go to the check-out counter. I show the clerk my gift card to have points credited and to be eligible for prizes."

- Instead of saying "to have points credited and be eligible for prizes," you can say "to have the points credited onto my gift card and qualify for prizes."

6) "Learn all the verbs included in the irregular verb list on page 206-207 of your course book. Complete all the exercises in Unit 3 from page 120 to 127 (or pages 120-127)."

- Instead of saying "Do all exercises Unit 3 from p. 120 to p. 127," you can use "Complete all the exercises in Unit 3 from page 120 to page 127 (or pages 120-127)." This makes the instruction clearer.

- Instead of saying "Study carefully the vocabulary on food on the photocopy," you can say "Study the food vocabulary on the photocopy carefully."

Overall, your sentences are mostly correct, but making these suggested changes will improve clarity and readability.