题目

Recent years have________the rapid development of the Internet and its influence on society and people. A．watched  B．observed C．witnessed  D．realized 答案：C 考查动词辨析。witness意为“目睹”。此处指目睹巨变。watch观看，注视；observe观察，注意到；realize意识到，实现。18．（1）等比数列{an}中，${a_3}=\frac{3}{2}，{S_3}=\frac{9}{2}$，求公比q的值．（2）已知数列{an}中，${S_n}={n^2}$，求数列{an}通项公式．