― How do you like your English professor?

― He has lots of interesting _____ abroad, and in a word, he is a teacher of rich ____.[ ]

A.  experiences, experiences

B. experience, experience

C. experiences, experience

D. experience, experiences

一容积为350ml的瓶内盛有300g的水，一只口渴的乌鸦为喝到水，衔石子投入瓶中，当投入20块石子后，水面恰好升到瓶口，若每块石子的平均质量为6.0g，求一块石子的体积和密度．