When Bill Gates decided to create Microsoft, he ________ law at Harvard University.
A．studied
B．had studied
C．was studying
D．would study
When Bill Gates decided to create Microsoft, he ________ law at Harvard University.
A．studied
B．had studied
C．was studying
D．would study
C
解析：句意：比尔·盖茨决定创建微软时，他正在哈佛大学学习法律。根据句意，语境中为过去时，表示在过去的一段时间内正在做某事，应用过去进行时，故选择C项。studied是一般过去时，没有体现出当时正在学习；had studied是过去完成时，表示在决定创建微软之前在哈佛学法律，不符合题意；would study表示过去常常。