for 和 since 在现在完成时中的应用
for与since都能与现在完成时连用,但区别较大: (1)for后须接“时间段” He has studied English for five years. 他学英语5年了。 (2)since后须接“时间点” He has studied English since 1999. 他从1999年开始学英语。