Question

       we were playing basketball on the playground, it began to rain.

A．While	B．After
C．Before	D．Since

Answer 1

A

试题分析：句意：当我们正在操场上打篮球时，开始下雨了。when,当，强调从句的动作发生时，主句的动作正在发生。while,强调从句的动作在发生的过程中，主句的动作发生了。根据句意，故选A。