题目

-Betty, hurry up! Your mother   _______  for you at the school gate.     -OK!    A. waited        B. waits        C. is waiting        D. will wait 答案：C如图，在Rt△ABC中，∠ACB=90°，∠A＜∠B，沿△ABC的中线OC将△COA折叠，使点A落在点D处，若CD恰好与MB垂直，则tanA的值为________．