A：Look! This is the flag of ____. Do you know?

B：Yes, I ____ about it. It has five yellow stars.

A：What is the capital ____ of China?

B：It's Beijing. Tian'anmen Square is in Beijing. It's ____  .

A：What do you ____ ?

B：Chinese.

A：Great！

读太平洋洋流分布图，回答下题．

—Wait ________ minute. I'll finish my work first.

在垂直于纸面的匀强磁场中，有一原来静止的原子核，该核衰变后，放出的带电粒子和反冲核的运动轨迹如图a、b所示，由图可知（   ）