1He spent at least as much time reading as you ______ online yesterday.
A．had to chat B．do chatting
C．had chatted D．did chatting
解析：此句补充完整为：He spent at least as much time reading as you spent chatting online yesterday.因为前面一出现了一次you spent...，为了避免重复，所以用did代替；spend的用法是：spend time (in) doing sth.，所以选用D项。
答案：D
