问题
选择题
Mario used to _____________ in the morning.
A．practiceswimming
B．practicingswimming
C．practiceswim
D．practicesswimming
答案
A
题目分析：考查动词短语。句意Mario过去常常在早上练习游泳。Used to 过去常常。Practice doing 练习做某事，故practise用动词原形。故选A项。