Anytime. It's really easy, but, like anything,
没问题。实在很容易 但是 和其它东西一样
There's no sense in going by boat when the plane is just as cheap and much quicker.
既然乘飞机和坐船一样便宜而且还快得多,那么就没有理由去坐船。
he realizes its volume, as the space that the shape displaces in the air.
他能意识到物体的体积,那就是它的形状在空气中所占的空间。