Definition: a round handle, or a round button on a machine Level: C1
他抓住黄铜门把手，打开了门。
He grasped the brass ___knob and opened the door.
转动黑色旋钮来打开收音机。
Turn the black ___knob to switch on the radio.
当我转动旋钮时，机器由于停电没有启动。
When I turned the ___knob, the machine didn't start because of a power outage.
