Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools. A) when it is known that humans made B) at which it is known that humans had made C) at which humans are known to have made D) that humans are known to be making E) of humans who were known to make 1:大家给看看这题考的是known这个用法吗,只知道known as Ving不对,要用known to V来代替,是不是known后面只能跟to,that从句也是不可以 2:date后面用什么词有什么讲究吗 大家给指点指点,谢谢 |