I left out two last sentences, Writeacher. Could you please check them?
1) I have no credit on my phone. I need to top it up.
3) They are trying out a new vaccine against cancer.
In American English..
I have no minutes left on my phone, I need to refill.
They are experimenting (or trying out) a new vaccine to (prevent) (cure) cancer. I am not certain of your purpose intended for the vaccine.
1. This is fine. I think "top it up" is a British phrasing that's not used in the US, but it's correct.
3. ... a new vaccine to prevent cancer.
Nice!
To check your sentences, you can follow these steps:
1) Read the sentence and look for any grammatical errors or typos. Make sure the sentence is clear and concise.
2) Check for correct sentence structure. Ensure that the subject and verb agreement is accurate, and there are no run-on or fragment sentences.
3) Review the use of punctuation. Check for proper capitalization, commas, periods, and other punctuation marks.
Now let's review your sentences:
1) "I have no credit on my phone. I need to top it up."
This sentence is grammatically correct and clear. It conveys the message that the person speaking has no credit on their phone and needs to recharge it.
2) "They are trying out a new vaccine against cancer."
This sentence is also grammatically correct. It states that someone or a group of people are experimenting with a new vaccine in order to combat cancer.
Both sentences seem fine and don't require any corrections. Well done!