1.The number of modern technology companies reached 18 during the 18th century and ______ around that level since.
A. are remaining 
B. have remained C. is remaining D. has remained
【答案及解析】 D
句意：18世纪，现代科技公司的数量达到了18所，此后一直保持在这个水平。ever since“从那以后”作时间状语，句子用现在完成时态。主语为The number of modern technology companies，the number of固定短语，“……的数目”，作主语时，谓语动词应用第三人称单数形式。故选D。
【总结】考查时态和主谓一致，本题涉及现在完成时和the number of的应用。
