Please be serious about what you do.这句话中的serious什么意思?好像不是“严肃”

Please be serious about what you do.这句话中的serious什么意思?好像不是“严肃” Please be serious. I am not _______. You should consider it carefully .Please be serious.I am not _______.You should consider it carefully be serious about diong about.=be serious about sth. be serious about什么意思? you cannot be serious是什么意思 you can not be serious! can not be so serious please be please be be serious about do还是doing? be serious about doing sth是什么意思? 用（be)serious about有翻译 you can't be serious是什么意思 I could not be more serious here NEED NOT BE SERIOUS是何意思? 求帮忙找一下这个的语法错误,把改好的发过来N:This a play of MH370,we are sorry about it,please everybody can be serious ,serious and serious.(N leave)A:Good evening Ladies and Gentlemen,Welcome to the flight from Malaysia to China.N Silence,please!Please be quiet!