Final answer:
The subjects in the sentence 'He turned the car around because she had forgotten her schoolbooks' are 'he' and 'she'. They are the ones carrying out the actions in the sentence.
Step-by-step explanation:
In the sentence, 'He turned the car around because she had forgotten her schoolbooks,' the subject(s) are 'He' and 'she'. In English grammar, the subject is usually the person, thing, or idea that is doing something or being something. In this case, 'He' is the subject of the main clause 'He turned the car around,' and 'she' is the subject of the subordinate clause 'because she had forgotten her schoolbooks.'
Learn more about subjects in English