He used to __(swim)when he was young.
A: swim
B: swimming
C: swam
D: swum
                    A: swim
B: swimming
C: swam
D: swum
举一反三
- —Where is Mike? —He’s _______ at the pool. A: swimming B: swim C: swam D: to swim
 - He enjoys ____. (swimming/to swim)
 - His favourite sport is _________ . A: swim B: swims C: swimming D: swam
 - There is a boy in the river. He ____ across the river. A: is swimming B: swimming C: swim D: swims
 - He never used to swim in winter,____?
 
