澳大利亚地形分为三部分: 东部是____ __,西部为___ ___,中部为___ ___。
山地,高原,平原
At the railway station,he waved goodbye to his friend until the train was ________.
A.out of sight
B.out of reach
C.out of order
D.out of place
低压空气阻尼式时间继电器又称为气囊式时间继电器,它是利用空气阻尼的原理配合微动开关来产生延时效果,JS7-3A型空气阻尼式时间继电器的气囊在()的位置。
A.2
B.3
C.4
D.5