用适当的介词或副词填空。

1. How are you getting____with your studies?

2. I'm not good____communicating____people.

3. These are the reasons____doing that.

4. They fell________love with each other two years ago.

5. Tom is becoming so crazy____playing basketball.

张某是某施工单位的材料采购员，一直代理本单位与甲建材公司的材料采购业务。后张某被单位开除，但甲公司并不知情。张某用盖有原单位公章的空白合同书与甲公司签订材料采购合同，则该合同为( )。

A．效力待定合同

B．无效合同

C．可撤销合同

D．有效合同