题目

It’s 8 o’clock. My mother is reading a book. My sister and I _____.A. is doing my homework B. am doing my homeworkC. is doing our homework D. are doing our homework 答案：【答案】D【解析】试题分析：句意：八点了。我母亲正在读书。我和姐姐正在做作业。主语my sister and I是复数形式，故谓语用复数。故选D。如图，∠AOP=∠BOP=15°，PC∥OA，PD⊥OA，若PC=4，则PD的长为 ．