Mass deaths of birds were not unheard of, but they normally happened unnoticed at sea or in rural areas away from towns. Many birds are weak and die in winter _______ food is scarce.
A.which | B.what | C.when | D.how |
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Mass deaths of birds were not unheard of, but they normally happened unnoticed at sea or in rural areas away from towns. Many birds are weak and die in winter _______ food is scarce.
A.which | B.what | C.when | D.how |