Nobody knows how people first came to these islands. They _____ from South America on rafts.

Nobody knows how people first came to these islands. They ______ from South America on rafts.

A. must have sailed　　　　　　　　　 B. can have sailed　　

C. might have sailed　　 D. should have sailed

Nobody knows how people first came to these islands. They _____ from South America on rafts.

Nobody knows how people first came to these islands. They ________ from South America on rafts.

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