题目

—I can't remember those grammar rules!—_________. Practice more. A . You're not alone B . It's hard to say C . I'm afraid not D . It's up to you 答案：A如图，△ABC 中，AB=AC=9 cm，∠BAC=120°，AD 是 △ABC 的中线，AE 是 ∠BAD 的角平分线，DF∥AB，交 AE 的延长线于 F，求 DF 的长．