为什么前面用to learn 而后面用learni...

为什么前面用to learn 而后面用learni... 为什么前面用to learn 而后面用learning呢?It took me two years to learn English.和I spend two years learning English.两句话,为什么前面用to learn 而后面用learning呢? All I have to do is learn English.这句里learn是动词,前面干吗用is I'm sorry not to have taken the advice he gave me.为什么前面是用的have taken 而后面用的GAVE?不理解.还请赐教! i cannot remember if i posted the letter 为什么后面用过去式而前面不用 The poor boy had difficulty walking为什么前面是has而后面用walking 为什么说in the ftont of 是在.前面,而在.后面直接用behind the That's why it's important to learn a second language.在这里second前面为什么用a learn English by listening to the radio.by后面的listen to 为什么用动词ing形式? She doesn't know whether to go or wait.为什么前面用的是to go,后面却用wait而不加to呢?原题是She doesn't know whether ______(go) or wait.go,但是为什么? 求分析此句 The goal is to be exposed to novelty and increasing levels of challenge为什么前面用的to be exposed to而后面用的increasing? 'didn't used to do sth' 为什么前面用了过去式后面还用used? how to learn English中为什么how后面加to I think the best way to learn English is by speaking 为什么用to learn 连接而不用learn或lerning连接强调的是为什么要加to /// （ ）a language requires time and effort in addition to talent.为什么用learning,而不可以用to learn或者learn呢.有点混乱呐 grow up healthy and brightly为什么healthy不用副词形式?如题,为什么后面是brightly而前面不是healthily,为什么可以说to grow up healthy,happy and proud,也就是说为什么都用形容词形式呢? prefer to do sth.rather than doing sth.为什么前面是to do而后面是doing.为什么前后不一致.这个句型的意思,用的场合.各位看看这个网页第九条. When he was in his fifties Marx began to learn English.我想问的是 为什么 WHEN HE 后面跟的是WAS 而不是IS?这个叫什么从句?是不是后面从句用什么时态,前面主句就要用同样的时态?