A、By digging site. B、By reconstructing skeletons. C、By observing them closely. D、By living with them. B文章中提到通过重组骨架，科学家能获知恐龙的生活条件

It was not until one hundred and fifty years ago that scientists learned about the existence of dinosaurs. Thanks to an English doctor and his wife, the door was opened to this zoological study. Reasoning that these animals’ tremendous size must have made them terrible creatures, scientists combined  two Greek words, deimos, meaning terrible, and sauros,  meaning lizards, to form the word dinosaur.
    After many years of study, they determined that these beasts roamed the earth for millions of years, and ceased to exist some sixty million years ago.
    Unbelievable as it may seem, not all dinosaurs were carnivorous, that is, meat eating. Many were herbivorous, or vegetarians.
    By reassembling the bones found at digging sites, scientists  have been able to reconstruct the skeletons and learn great deal about the dinosaur’s living conditions. They have learned that dinosaurs inhabited not only the land, but also the water and sky.