题目

By careful observation and precise calculation, Nicolaus Copernicus _____ that there is no one center in the universe and the sun is the center of the solar system.    A. believed    B. thought   C. concluded   D. imagined   答案：CHe had sent for a doctor; ___ we did our best to nurse the patient.A．in the same time B．on the other handC．meanwhileD．during which time