She will go fishing as soon as her mother - (come)back.横线处填c

come原型。as soon as 后面接一般现在式或者是一般过去式的从句,至于要哪个要看前面那里用什么式,这里She will go ,明显是将来时的,是要在mother come back之后的,这个要用一般现在式。我印象中是这样。