最易并发脑栓塞的是
A．主动脉瓣狭窄
B．高血压，动脉硬化
C．二尖瓣关闭不全伴心房颤动
D．心力衰竭
E．二尖瓣狭窄伴心房颤动
参考答案：E
In order to learn the _______ of the family business, Bill took a job as messenger boy in one of the offices.
A．ins and outs
B．dos and don’ts
C．heads and tails
D．t’s and i’s
苹果和梨均属于跃变型果实，因此用于长期贮藏的果实采收的适宜时期是：（）
A、跃变之前
B、跃变高峰
C、跃变之后
