A:①②③
B:②③④
C:①②④
D:①③④
史书记载:“水激轮转,众筒兜水,次第下倾于岸上……以灌稻田,日夜不息,绝胜为力。”这种提水灌溉工具出现于( )
_____ Amy met Peter, she with her mum _______ for the bus at the bus station.
直角三角形两个锐角之和为____ 度.