题目

—When did the mother _____ her husband’s letter?—She _______ a letter from him since last Friday.A. receive, has heard B. receive, has hadC. hear from, has heard D. receive, has received 答案：【答案】B【解析】句意：----母亲什么时候收到丈夫的信的？-----自从上星期五以来，她收到了他的一封信。考查动词辨析。1.receive：收到…，瞬间动词；2.hear from：收到…的来信，瞬间动词；3.have a letter from：收到…来信，和时间段连用，延续性动词。根据句意可知第一个句填receive或hear from；根据since l做匀变速直线运动的质点，在第1s内的位移是3m，第2s内的位移是5m，则该物体的加速度是__________m/s2，第2s末的瞬时速度为__________m/s。