因为arrive是不及物动词,后面可以不加宾语的,所以用arrive
相比之下,reach却一定要加宾语的
When will you arrive tomorrow?
When will you arrive in Shanghai tomrrow?
When will you reach Shanghai tomorrow?
arrive in之类的话,一定要加地点,例子上面已给出.
get to 也是一样的道理