单纯性二尖瓣狭窄的病变不伴有
A．左心房肥厚B．左心房扩张C．右心室肥厚D．左心室肥厚E．心脏呈梨形
参考答案：D
When we realize yesterday is gone forever, we find we are growing up ______. [ ]
A. little by little
B. step by step
C. one by one
D. side by side
从1，2，3，…，20这20个自然数中，每次任取3个数，若其和是大于10的偶数，则这样的数组有______个．
