听力里面的句子:And how strong is the evidence that climate change is happening that it's really something we need to be worried about?请问happening后面的that引导的是什么从句?
The conventional theory is that people yawn when bored or sleepy because yawning raises blood oxygen levels, which in turn raises alertness.whchi in turn 在这里不是否定吧?是进一步吗?