辨识国旗，选择正确的颜色单词填空。

1. Sarah's flag (旗) is ____________.[ ]

A. red and white

B. yellow and green

2. Wu Yifan's flag (旗) is ____________.[ ]

A. red and white

B. yellow and red

3. John's flag (旗) is ____________.[ ]

A. red, green and white

B. blue, red and white

4. Mike's flag (旗) is ____________.[ ]

A. blue, red and white

B. black, white and yellow

灯质AlRW表示（）。

A.互光灯，一个周期内红、白交替发光，常明不灭

B.闪光灯有红光弧和白光弧

C.一个周期内交替闪一次红光和一次白光

D.闪白光和闪红光