在真核生物中，多种生长因子调节各组织细胞的生长、分化和增殖，生长因子的受体通常具有的酶促活性是（）

A．酪氨酸激酶

B．丝氨酸一苏氨酸激酶

C．磷酸水解酶

D．蛋白水解酶

E．酯酶

根据各组对话内容，从下面方框里提供的5个选项中选出最佳选项

A: Could I use your dictionary. pleaseB: ().A: Thank you. I’ll return it as soon as possible.

A．Sure. What is it

B．It’s very nice of you to say so.

C．It’s nothing.

D．Have a nice trip!

E．Certainly. Here you are.