题目

—Excuse me. Could you please not smoke here?—________.A．Sorry, I won’tB．No problemC．You’re welcomeD．It doesn’t matter 答案：A解析:略如图，正方形ABCD中，M为BC上一点，F是AM的中点，EF⊥AM，垂足为F，交AD的延长线于点E，交DC于点N．（1）求证：△ABM∽△EFA；（2）若AB=12，BM=5，求DE的长．