D.
since和時(shí)間點(diǎn)連用表時(shí)間段.joined過去式表示這一動(dòng)作發(fā)生在過去某一時(shí)刻.
主句用完成時(shí),也就是：
l have known Dr jackson since she joined the chinese society.題目沒有提及時(shí)間點(diǎn)??？時(shí)間點(diǎn)就是she joined the chinese society的時(shí)間呀完成時(shí)應(yīng)該是had joined才是標(biāo)準(zhǔn)的完成時(shí)?。课抑雷穯枩p慢了您的得分速度，所以又加了100分had joined是過去完成時(shí)；have/has done是現(xiàn)在完成時(shí)。這題用的是現(xiàn)在完成時(shí)。得分固然重要，把問題解釋清楚，能夠?qū)δ阌袔椭匾?謝謝!