選B
reach作為到達(dá)講時(shí)是及物動(dòng)詞,其后必須跟賓語(yǔ),如When will they reach Beijiing?他們什么時(shí)候到達(dá)北京?
而在此句中,here 是副詞,在句中做狀語(yǔ),不是賓語(yǔ),所以不能用reach.只能用arrive,它是不及物動(dòng)詞,后面接賓語(yǔ)時(shí)須加介詞at或者in.大地方用in,小地方用at.
比如：They will arrive in Beijing at six o'clock.
They will arrive at the school at six o'clock.
此句中here是副詞,作狀語(yǔ),arrive后面無(wú)須加in或者at,直接用不及物動(dòng)詞arrive加副詞即可.
其他例子還有：When will they arrive there?
When will you arrive home?
there,home均為副詞.
所以本題選B