When did scientists discover that oysters were in danger? A. In the early part of the 19th century B. At the beginning of this century C. In the 1940's D. Just recently

B

Theo thông tin trong bài “Until recently; the supply of wild oysters and those crudely farmed were more than enough to satisfy people's needs. But today the delectable seafood is no longer available in abundance. The problem has become so serious that some oyster beds have vanished entirely”®các nhà khoa học phát hiện rằng loài hàu đang gặp nguy hiểm ở trong đầu thế kỷ này.