单选题 In the background was that eternal hum
A. long
B. never-ending
C. boring
D. extensive

【正确答案】 B
【答案解析】eternal和never?ending都有“永恒的”意思。long是“长的”，boring是“乏味的”I found his talk rather boring. 我发现他的报告相当乏味。extensive是“广泛的”。