问题
单项选择题
In areas covered by Inmarsat HF can be used as an（）to satellite communications.
A.alternation
B.alternate
C.alter
D.alternative
答案
参考答案：D
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In areas covered by Inmarsat HF can be used as an（）to satellite communications.
A.alternation
B.alternate
C.alter
D.alternative
参考答案：D