第一个空是at which 第二个空填where
因为,前面是一个定语从句,先行词“the place”在从句中做地点状语,连成一句话是:the bridge is supposed to be built at the place,所以除了用关系副词where之外,还可以介词提前的形式:at which(介词后不能用that);后面的从句是一个地点状语从句,所以就用where。
The place_ where__the bridge is supposed to be built should be __where__the cross-river traffic is the heaviest.
在这里, "the place"是地点名词,所以要用"where" 来引导。 在 “that/which the cross-river traffic(主语) is(谓语) the heaviest.” 中,where是做“the place should be”的表语从句引导词。
不知道