植入开始的时间是（）。
A、受精后第5-6天
B、受精后第2-3天
C、受精后第1-3天
D、受精后第11-12天
参考答案：A
--Surfing first started on the islands of Hawaii, didn't it?
--Yes, but now it ______ by people all over the world.
A．is enjoyed
B．is enjoying
C．has enjoyed
D．will enjoy
简述操作台上的按钮部分。
