Things have changed a lot since I was a child.

A. gradually         

B. suddenly            

C. frequently           

D. greatly

They converted the spare bedroom into an office.

A. reduced           

B. turned              

C. moved               

D.reformed

A number of theories have been proposed to explain the situation.

A. suggested        

B. tested               

C. used                 

D.announced

His long-term goal is to set up his own business.

A. idea               

B. energy              

C. aim                  

D.order

We explored the possibility of expansion at the conference.

A. offered           

B. investigated         

C. included             

D. accepted