for
是介词，其后要跟名词，当后面出现动词时就需要变形为动名词ing形式
其实这是介词类的普遍规律用法，其他介词还有about,in,on,at,from,off等等．
给你简单举例一下：同一句话
”到吃晚饭时间了”
可以说It's
time
for
supper
.
也可以说It's
time
for
having
dinner
.
it's
time
to
do
sth.
it's
time
for
sb.
to
do
sth.
it's
time
for
sth.
it's
time
for
doing
sth.
反正for是介词,后面要么跟名词,要么跟动名词(v.ing)
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