题目内容
Polar bears live mostly on ________ sea ice, which they use as ________ platform for hunting seals.
[ ]
A.a; a
B.a; the
C.不填; a
D.the; 不填
答案:C
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题目内容
Polar bears live mostly on ________ sea ice, which they use as ________ platform for hunting seals.
A.a; a
B.a; the
C.不填; a
D.the; 不填