Có đoạn văn như sau:
About 200 million years ago, as the Triassic Period came to a close, many species of animals disappeared from the face of the Earth. Scientists previously believed that the series of extinctions happened over a period of 15 to 20 million years. Recent discoveries is Nova Scotia suggest, however, that the extinctions may have happened over a much shorter period of time, perhaps less than 800000 years.
Cái câu tô đỏ đó, tại sao lại thế nhỉ vì sự tuyệt chủng này xảy ra mấy nghìn năm trước, sao ko dùng là may happened mà là may have happened.
Mọi người cho ý kiến nha!