一段英語短文的中心句的問題-----------高手幫忙
There is an old saying in English:“Laughter is the best medicine”.Until recently,few people took the saying very seriously.Now,however,doctors have begun to investigate laughter and the effects it has on the human body.They have found evidence that laughter really can improve people’s health.
第1：有人說引號里面的是中心句“Laughter is the best medicine.”
第2：有人說however后面的是中心句“doctors have begun to investigate laughter and the effects it has on the human body”
第3：有人說found evidence后面的同位語從句“l(fā)aughter really can improve people’s health”是中心句.
暈了,都說的很有道理,到底哪段是中心句,說明道理.