Complete each of the following sentences with a (compound) word derived from the one(s) given in brackets.
Men’s never-ceasing search for knowledge continues to （ ）our understanding of the earth’s atmosphere. (broad)
【正确答案】：BROADEN
【题目解析】：
句意：人类对知识永不停息的探索，不断拓宽我们对地球大气层的理解。broaden拓宽。