请教三道SAT语法题1.The Stegosaurus,(plant-eating dinosaurs) with (p

请教三道SAT语法题
1.The Stegosaurus,(plant-eating dinosaurs) with (protective) bony plants and tail spikes,was (once common in) (what is now) Colorado.为什么不选B改为Protectively呢?
2.An amateur (herself),the accountant offered (to help) the artist with his business accounts,complicated (as they were) (by) his unusual system of record keeping.
可是为什么我觉得应该把by改成as,
3.Some experts say (that of all) the musical forms that constituted African music in the second (half of the) twentieth century,Congolese rumba and its rambuctious offsprings,soukous,(were) the (more) influential.