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Do you often work late _____ night.
A．at
B．in
C．for
D．during
_____ a cold morning, he left for his hometown.
[ ]
A
B
C
D
________ a cold morning, he left for his hometown．
A．In
B．At
C．On
D．During
________ those two years he studied maths very hard.
A．During
C．In
D．For