1.我們的領導人常常參加體力勞動，給我們樹立了良好的榜樣。原文翻譯：He took an active part in revolutionary activities and was a one of the labour movement at that time.請問，首先這句話中為什么有“took”出現，其次，“at that time”，能起到什么作用？？？
做修辭的．做：常常 解釋．
