[问答题] 简述微笑的特征。

When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer mating in the （） [""slow" direction, just before the 12 o'clock position",""fast" direction, just after the 12 o'clock position",""fast" direction, just before the 12 o'clock position",""slow" direction, just after the 12 o'clock positio"] 怎样选择拍摄角度？ （）是危害最大的一种磨损，是机械过早损坏的主要原因之一。 ["粘着磨损","磨粒磨损","接触疲劳磨损","腐蚀磨损"] 社区学院负责管理学生安装了Windows 7的笔记本电脑。你要防止学生使用FTP上传文件到Internet上的FTP站点，但是允许他们使用SMTP协议发送出站e-mail。你将配置以下哪一规则达成这一目标？（） ["入站规则","出站规则","隔离规则","认证豁免规则"] 怎样在摄影中测定镜头视角？ 简述微笑的特征。