The left wing dipped until it was perpendicular to the ground.左翼下垂至与地面成90度角。Are the lines perpendicular to each other?这些直线相互垂直吗？The two lines of bones are set perpendicular to one another.这两排骨头相互垂直....
The national flag is billowing in the breeze.国旗在微风中飘扬.On the vast fields, one sees nothing but the wheat billowing in the wind.在辽阔的原野上, 但见麦浪随风起伏.A field of burning grass is billowing thick black clouds of smoke into the ...