题目

—What is your daughter doing now? —She is on the phone，________with one of her schoolmates，though they've just separated from each other. A．to chat                      B．chatting C．chatted                      D．being chatted 答案：B chat与逻辑主语she之间是主动关系，故用chatting作状语，表示伴随情况。16．如图，△ABC是边长为1的等边三角形，BD为AC边上的高，将△ABC折叠，使点B与点D重合，折痕EF交BD于点D1，再将△BEF折叠，使点B于点D1重合，折痕GH交BD1于点D2，依次折叠，则BDn=$\frac{\sqrt{3}}{{2}^{n+1}}$．