请教０５０５语法２２.２４.３１题，大家侃侃～

２２．at present, about 300 (different) varieties( of dinosaur )have been identified from (bones found )on (every)  of the continents.选Ｄ，Ｄ是不对，但Ｂ也应该加＂Ｓ＂啊？

２４.   (by using)  special equipment ,seismologists( can determine )the size and location of (an) earthquake and fault( to) which it originated.选Ｄ，该怎么改呢？该成from吗？

３１.by 1996,the united states popultation (exceeded) 261 million ,with a median (age of) thirty-four ,(making it) one of the oldest national (population) on earth.选Ｄ，　应该怎么该呢？我觉得Ａ也错，应该改成has exceeded?

22题我也觉得dinosaur应加S,不过也不确定

24改成 from, origine from固定搭配

population可数不可数都可以,这里加s.by 1996 表过去时间,可以用过去时态的