用适当的介词填空。

1. How many minutes are there ______________ an hour?

2. I'll give my friend a present ______________ her birthday.

3. There are so many people ______________ China.

4. The girl asks her teacher ______________ helping.

5. We often go to school ______________ bus.

律师丁某在代理一起民事诉讼案件时，编造了一份对自己代理的一方当事人有利的虚假证言，指使证人卢某背熟以后向法庭陈述，致使本该败诉的己方当事人因此而胜诉。丁某的行为构成( )。

A．伪证罪

B．妨碍作证罪

C．帮助伪造证据罪

D．诉讼代理人妨碍作证罪