问题描述：
-You have been quite busy the whole afternoon.
-Yes,I_____on my homework and it will take another twenty minutes or so
A.have worked
B.am working
C.have been working
D.will be working
-Yes,I_____on my homework and it will take another twenty minutes or so
A.have worked
B.am working
C.have been working
D.will be working
问题解答：
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