b) 6.6.10.1 What are you
doing: this evening?
tomorrow morning? on
Saturday morning? on Sunday
evening? Tell your partner.​

Вопрос про ваши планы на ближайшее будущее, поэтому нужно использовать Present Continuous (как в вопросе)

What are you doing this evening?

I'm watching a new comedy this evening.

What are you doing tomorrow morning?

I'm seeing the doctor tomorrow morning.

или

I'm doing my homework tomorrow morning.

What are you doing on Saturday morning?

I'm helping my parents to tidy up our flat.

What are you doing on Sunday evening?

I'm going to visit my grandparents.