碱基与戊糖间是C-C连接的是（）核苷。

A young man was going to join the army (军队) and had to (41) a medical examination. The doctor was sitting at a desk when he came in. He said to the man, "Take your coat and shirt off and (42) on that chair.
The young man did so. The doctor looked at him for a moment without (43) up from his chair and then said, "All right. Put your clothes on again.
"But you haven’t examined me at ail!" the young man said in (44) .
"There is no need to do so," the doctor said with a (45) .
"When I (46) you to take your coat and shirt off, you heard me all right, so there is nothing wrong with your (47) . You saw the chair, so your eyes are (48) . You could take your clothes off and sit on the chair, so you must be in good health. And you understand what I told you to do and did it without a (49) , so you (50) healthy enough for the army.\

[A] pity[B] smile[C] pleasure

下面哪些命令或操作可以让用户从其他视图退回到用户视图（）.

A.quit

B.home

C.return

D.exit

透镜在生活中应用广泛，投影仪的镜头、放大镜都用到了                透镜（选填“凸”或“凹”），不同的是投影仪成的是                  像，放大镜成的是                 像（均选填“虚”或“实”）。

下列关于重力加速度的说法，正确的是（　　）

A．重力加速度的方向是垂直向下

B．在地球上不同的地方，重力加速度的大小都相同

C．在地球上同一地点，一切物体做自由落体运动的加速度都相同

D．重力加速度的大小由物体的重力决定

改革不能说是中国的第二次革命，因为改革和革命是有根本区别的。()