中小学校的非营业性互联网上网场所，应当为未成年学生提供（）的上网服务。
A.关于学习
B.课外辅导
C.适宜
D.健康有益
参考答案：D
有关开瓣音正确的是（）
A.出现于心底部
B.音调低
C.开瓣音提示瓣膜弹性和活动性尚好
D.S后0.08秒
E.历时较长而响亮
— How long have you been here?
— Only about five minutes. Henry and Simon _____ here with me. [ ]
A. have walked
B. had walked
C. walked
D. were walking
