11. B

12. D

1. are playing - have played

2. hasn't gone - bought - take

3. are going - will be

4. have written - came - haven't finished.

133. A
134. B
135. C
136. B
137. B
138. C
139. C
140. D
141. C
142. B
143. B
144. B
145. D
146. C
147. B
148. D

`6xy .2x^3 yz = 12x^4y^2z`

a, `x^2-2x+1=4`

`<=>(x-1)^2=2^2=(-2)^2`

`<=> [(x-1=2),(x-1=-2);}`

`<=> [(x=3),(x=-1):}`

b, `16-(x-3)^2=0`

`<=>(x-3)^2=4^2=(-4)^2`

`<=> [(x-3=4),(x-3=-4):}`

`<=> [(x=7),(x=-1):}`

2. I'm going to study in Australia. :v

1. The cupboard has 15 jars.
2. I'm going to studying in Australia.
3. It is difficult to solve this problem.

4. Will you come to have lunch with me ?

5. Liz occasionally goes dancing.