题目

 Mrs. Li explains English grammar so_____ that even I can understand it.        A. clear                      B. clearly                   C. more clearly         D. good 答案：B如图，已知CE、CF分别平分∠ACB和△ABC的外角∠ACG，EF∥BC，EF交AC于D．（1）判断△ECF是什么三角形，并说明理由；（2）试说明CD是△ECF的中线；（3）请探究∠ACB等于多少度时，CF=EF．