Yet用于句首是否要加“,

Yet用于句首是否要加“, although 是否不一定用于句首 yet的用法,出用在现在完成时中可否如下那样放在句首,为何?yet前后是否要加逗号?例：The sweat ran down his face and his eyes were glassy from his fever.[Yet] he looked straight ahead and kept running. 为什么过去完成时的否定句里面要加yet never,ever,already,yet,justnever用于___句,ever用于___句,already用于___/___句,yet用于___/___句,just用于___/___句. yet和still是否必须用于现在完成时yet和still到底是否必须用于现在完成时 哪什么时候用什么时态? yet用于（ ）句和 （ ）句表示仍然的意思,用于句（ ） 现在完成时中yet的用法?yet是不是既用于否定句,也用于特殊疑问句,一般疑问句呢? yet用于什么时态 可以放在句首吗如Yest it is incorrect.这样说是否正确?yet后是否要加逗号 already、yet、ever分别用于什么句?就是它们分别用于肯定句、否定句、疑问句的. yet在现在完成时中是否都是放在句末 already,yet 用于什么时态 yet只用于现在完成时吗 have you finished already?为什么不用have you finished yet?have you finished already?为什么不是have you finished yet?我老师说过already 用于肯定句中,yet用于否定句和一般疑问句 I____ don't understand what you said.A. stillB.yetC. already D. alsostill 用于肯定句,yet 用于否定句,可此题为何选A 理所当然造句,一个用于句首,一个用于句末 理所当然【用于句首】 【用于句末】根据提示 造句