什么是imperative tense

什么是imperative tense 什么是 imperative sentences imperative imperative 什么是simple present tense or present progressive? 为什么是It is imperative that this mission not fail.而不是It is imperative that this mission don't fail. imperative是什么意思 imperative是什么意思 imperative是什么意思 imperative是什么意思 imperative是什么意思 imperative是什么意思 imperative style 英语It is imperative that this mission not fail为什么是It is imperative that this mission not fail.而不是It is imperative that this mission don't fail. present countinuous tense是什么时态?如果是现在进行时为什么是express futurity it is imperative that? strategic imperative什么意思 categorical imperative是什么意思