Question

1.Have you known Dr.Jackson for a long time?yes ,since she -

Answer 1

1 D完成时句子中常跟since/for等状语,since引导的时间状语从句中用一般过去时,表示在过去某个时间内做的事、动作,所以选joined（过去时）2 C几倍于 twice/three times/four times as ..(形容词原形） as..vegetables...