白果的别名是（）
A.庄黄
B.银杏
C.血见愁
D.廑虫
E.千张纸
参考答案：B
I _________ him before. But my friends _________ him two days ago. [ ]
A. didn't meet; met
B. haven't met; met
C. don't meet; meet
D. hadn't met; meet
妊娠20周时，胎动的频率约为( )
A．1～2次/小时 B．3～5次/分C．3～5次/小时 D．18～20次/小时
