题干
She can’t help ______ the house because she’s busy making a cake.
A：to clea
B：cleaning
C：cleaned
D：being cleaned
答案(点此获取答案解析）
A
+
=1上一点P到左焦点F1的距离为2，M是线段PF1的中点，则M到原点O的距离等于 （ ）
