----  I will go to the countryside to see my grandmother this afternoon, so I can't go swimming with you .    

------ ______ .    [ ]

A. It' s my pleasure .      

B. You are welcome .    

C. That 's a pity.        

D. Sure , I am..

在美国，（）仍然占据全国定性研究总量80%的份额。

A.资料调查

B.问卷调查

C.小组座谈

D.实地观察