sth.is sth.,and is sth.和 sth.is sth.,and it is sth.哪个正确?（sth.= something）如题,请问上述两种说法哪一个是正确的表述

问一个英语语法问题he is doing sth and doing sth还是he is doing sht and is doing sth sth.is sth.,and is sth.和 sth.is sth.,and it is sth.哪个正确?（sth.= something）如题,请问上述两种说法哪一个是正确的表述 sth is be on sth is better believe This is sb's sth中对sb's提问 take sth to sb and Bring sth to sbwhat is the difference what is the difference between 'seem to do sth' and' seem doing sth'? what is the difference betyeen 'enjoy to do sth.' and 'enjoy doing sth.'? what's the difference between start to do sth and start ding sth?for exaple?i am totally confused who can tell me what is it exact difference? it is one’s duty to do sth句式仿写快 sb's job is to do sth 是对的还是sb's job is sth是对的? sth is shown和sth is showing有什么不同 sb.is up to sth. sb.is up to sth. is he do/dong sth? she is sth.with sb. sth is after you是什么意思? sth and sth后面的动词是用单数还是复数例如flowers and fruit 是用is还是are？