The conventional theory is that people yawn when bored or sleepy because yawning raises blood oxygen levels, which in turn raises alertness.whchiin turn 在这里不是否定吧?是进一步吗?
As a result, she says, some of theinjuries associated with
running, such as runner’s knee, are uncommon among race walkers.请问这里的 are 是与哪个主语保持一致?这样的问题如何定位主谓一致?
This is the question about which we've had so much discussion这句话中为什么要有个介词about?Everything that he said seemed quite reasonable这句话中为什么又没有介词了?介词什么时候,用什么时候不用??
下面这两句话中的 over 分别是什么词性?为什么?So far in Wuhan, over 200 illegal wharves have been shut
down.the Wuhan
goverment have shut down over 200
illegal wharves so far.