亲和素-生物素化碱性磷酸酶复合物的制备是将亲和素溶液与生物素化AP按多少浓度比反应后制得（）

A.1：1

B.2：1

C.3：1

D.4：1

E.5：1

用括号内所给动词的适当形式填空。

1. Look! The bus ______ (come).

2. He ______ (not go) home yesterday afternoon.

3. ______ you ______ (find) work in Hefei last year?

4. Tom usually ______ (walk) to school.

5. The moon ______ (move) round the earth.

6. The children ______ (watch) TV at home every evening.

7. —What ______ you ______ (do) tomorrow?

    —Nothing much.

8. —Where is Jim?

    —He ______ (mend) his bike in the garden.

9. Alice ______ (write) two letters to her parents last week.

10. We ______ (visit) you next Sunday.