1 heard from
receive a letter from = hear from 收到……来信.
2 not as/ so .as ……不如……
过去进行时表示过去的某个时间正在进行的动作,常见时间状语有 at this time yesterday; at nine last night 等,而一般过去时表示过去某个时间发生了的动作,时间状语有yesterday; two days ago ,last night ,in 1998等
如 He was doing his homework at nine last night .
He did his homework two minutes ago .
在那时 at that time
加油!不明白再问!