_____ ashes from the volcano in Iceland have caused problems for air traffic and business, scientists don't think it will have long-term effects on human health.
A.Since | B.As | C.While | D.Because |
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_____ ashes from the volcano in Iceland have caused problems for air traffic and business, scientists don't think it will have long-term effects on human health.
A.Since | B.As | C.While | D.Because |