A.只有紅燈長(zhǎng)亮 B.只有黃燈長(zhǎng)亮 C.紅燈長(zhǎng)亮且黃燈閃亮 D.紅燈閃亮且黃燈閃亮
A.S1 B.S2 C.S3 D.S4
A.4mm B.5mm C.6mm D.7mm