敷设在桥梁上的燃气管道应采用加厚的无缝钢管和焊接钢管，尽量减少焊缝，对焊缝应进行 (

用适当的介词填空。

1. Liu Hang sits _______ the right side of the classroom. Li Gang sits in the front.

    Zhang Xia sits next _______ him.

2. —Do you sit _______ the center of the classroom?

    —No, I sit on Meimei's right. We sit _______ the front now.

3. Look _______ the picture. There is a pig _______ it.

4. Can you see the blackboard _______ the wall?

    My teacher is drawing a tree _______ it.

5. There are some public phones _______ the street.

6. You can see the post office _______ the corner of the street.

7. There is a bird _______ the sky (天空).

8. My mother gets home _______ 6 o'clock every afternoon.

You and I could hardly work together，________？[ ]

A．could you  

B．couldn’t I

C．couldn’t we  

D．could we

棒材生产中冷床的作用是矫直和（）钢材的。

下列程序的执行结果是( )。
Function P(N As Integer)
For i=1 To N
Sum=Sum+i
Next i
P=Sum
End Function
Private Sub Command1_Click()
S=P(1)+P(2)+P(3)+P(4)
Print S;
End Sub

A．15

B．16

C．20

D．25

下图为甲病（A—a）和乙病（B—b）的遗传系谱图，且甲乙两种遗传病至少有一种是伴性遗传病，请回答下列问题：

如果Ⅰ-1患有神经性肌肉衰弱，控制该病的基因位于线粒体上，则在Ⅲ代中可能患有该病的个体为（）（填序号）