Question

【题目】According to Charles Keeling, the amount of carbon dioxide ________ sharply and steadily over the forty years between 1957 and 1997.

A. increased B. had increased

C. had been increased D. was increasing

Answer 1

【答案】A

【解析】

试题分析：句中的时间状语over the forty years between 1957 and 1997是过去的时间状语，所以用一般过去时。故选A。