5．We have several a________to choose from.

4．Husband and wife should s________roles with each other occasionally.

3．The officer c________his men to fire.

2．When I got to the railway station，they were l________the truck with bananas.

1．Oil is Kuwait’s most important natural r________.

6. 已知a、b、c均为实数，且=c。

化简。

5．对于题目“化简求值：+，其中a=”，甲、乙两个学生的解答不同．

　　 甲的解答是：+=+=+－a=

　　 乙的解答是：+=+=+a－=a=

　　 谁的解答是错误的？为什么？

4.已知x=+1，求()÷的值．

2.计算：(3+。

3(.如图所示，实数a，b在数轴上的位置，化简．

1.计算：+(－)+。