4. she making a cake at 7 pm yesterday? — Yes, she / No, she

4. she making a cake at 7 pm yesterday? — Yes, she / No, she

Согласно грамматике английского языка, необходимо вставить вспомогательный глагол перед подлежащим, чтобы образовать вопрос в Past Continuous (прошедшее продолженное время).

В данном случае, подлежащее - she, поэтому используем вспомогательный глагол was.

she making a cake at 7 pm yesterday? - Was she making a cake at 7 pm yesterday?

Yes, she / No, she - Yes, she was / No, she wasn't.

Ответ: Was she making a cake at 7 pm yesterday? — Yes, she was / No, she wasn't