750立方厘米=____立方分米

20分=____时

短文填空

    One ____(rain) night I was driving along a lonely highway ____I saw a man walking rapidly ahead of me along the side of the road.It was pouring rain and I slowed down to avoid splashing him as I went by.

    He misunderstood and thought I was offering a ride，and ran towards my car. He was very tall and had a full beard, ____ scared me. I stepped on the gas pedal  ____（leave）quickly and I saw the look of total despair in his eyes. Suddenly，all fear was  ____(go) and I backed up and unlocked my car door，praying this was not the ____(big) mistake in my life but somehow knowing it would be okay.

    The man's truck had got stuck ____the mud. He ____(walk) for miles.No one would pick  ____up and his wife was giving birth to their first child in the hospital. He had cried at the thought that he might not be there. ____ fortunate), we arrived in the hospital before his son was born.

 ①以原点O为对称中心，画出△ABC关于原点O对称的△A₁B₁C₁，并写出B₁的坐标；

 ②再把△A₁B₁C₁绕点C₁，顺时针旋转90°，得到△A₂B₂C₂，请你画出△A₂B₂C₂，并写出B₂的坐标．