B. to see whether pigeons can be trained as help to find as后面的help的主语是谁不清楚 C.to see if pigeons can be trained for helping to find 不用if D.that see if pigeons are able to be trained in helping to find 同上 E.that see whether pigeons are able to be trained for help in finding be able to 表示本身具有能力做某事 “for help in finding”繁琐