____
① What are you doing? ____ A. No,she isn't.
② What is your mum doing? ____ B. Yes I am.
③ Can I use your pen? ____ C. I'm cleaning my room.
④ Is Sarah reading a book? ____ D. She is cooking fish.
⑤ Are yoy doing homework? ____ E. Sure.
关于限制性核酸内切酶的叙述,错误的是
请用句子中划线的词造句。