——When did you buy this computer? It looks so new.——I it for only a couple of days. My sister bought it for me as a birthday present.
A:bought
B:have bought
C:have had
D:had
将矩形纸片ABCD按如图所示的方式折叠,AE、EF为折痕,∠BAE=30°,AB= ,折叠后,点C落在AD边上的 处,并且点B落在 边上的 处.则BC的长为( ).