sally has been swimming _____four hours 1.for about 2.since 3.about 4.in
问题描述：
sally has been swimming _____four hours 1.for about 2.since 3.about 4.in
答
A
for +一段时间,与现在完成时连用
注：SINCE +过去的时间点,也是与完成时连用,如 since four hours ago
加油!不明白再问!