I will arrive at once if neccessary.

When will the train ___? A arrive B arrive at C arrive in D reach

A arrive\u4e0d\u53ca\u7269\uff0c\u4e0d\u8ddf\u5730\u540d\u65f6\u76f4\u63a5\u7528\uff0c\u8ddf\u5730\u540d\u65f6\u5c0f\u5730\u540d\u540e\u52a0at \uff0c\u5927\u5730\u540d\u540e\u52a0in\uff0creach\u53ca\u7269\u52a8\u8bcd\uff0c\u540e\u9700\u52a0\u5730\u70b9\u540d\u8bcd

arrive \u52a9\uff0cbe\uff0c\u60c5\u540e\u7528\u539f\u578b

get to 和reach是及物动词所以不能单独使用做谓语，但是ARRIVE是不及物动词，可以不接宾语直接做谓语，AT ONCE 在这里是状语，立刻马上的意思。

reach 与 get to 后面要加地点才能组成一个句子，
arrive是不及物动词，可以直接用成主语+arrive
希望可以帮到你！

arrive是不及物动词,所以后面的成分是从句，如果是reach或者get to的话，后面要添上the place

因为arrive 后面没有地点名词，而且根据句子的意思我们可以猜测到arrive 后面的词应该是here,或there,这两个词是副词，arrive at,要省略介词at.

at once 相当于right away 意思是马上 修饰arrive

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