A huge flying reptile that died out with the dinosaurs some 65 million years ago, the Quetzalcoatlus had a wingspan of 36 feet, believed to be the largest flying creature the world has ever seen. A. believed to be C. and it is believed to have been
为什么需要用to have done? 答案解释的是因为Q已经died out ,表明这种动物曾经是最大的动物,但现在已经不存在了,而A则暗示了这种动物现在还是最大的动物,与die out 矛盾!
但是,我认为, the world has ever seen 暗示从过去持续到现在世界的情况还是如此,所以Q还是可以是迄今最大的, 请各位指教!