原式=（22+3）（22-3）
=（22）2-（3）2
=8-3=5．
石英晶体振荡器是利用石英晶体的压电效应和逆压电效应工作的，其频率稳定度很高，通常可分为（）和并联型晶体振荡器两种。
______ studies how sentences in spoken and written language form larger meaningful units such as paragraphs, conversations, and interviews.
A．Communicative Language Teaching
B．Meaning negotiation
C．Discourse analysis
D．Pragmatics
