1
do
sth是一般现在时态,比如she
often
do
homework[她经常做家务],
构成:主语+形容词+事/主语+often/usully/always/sometimes/neve等+事
2
to
do
sth中重要的是to,to用语两个动词之间,列如she
asks
me
to
do
homework。
ask是动词,do也是动词,那么之间要加to.
3
doing
sth是现在进行时或句中
有like.比如i
like
playing
games[我喜欢玩游戏]
现在进行时标志词有now
,at
the
present
,at
the
moment
等,比如i'm
looking
foe
a
book[我在找一本书]
构成:主语+动词be[am
is
are]+动词ing[现代分词]
希望我解释的能让您明白。