The old pianist wouldn't listen to our repeated request that he ________ in public again.[      ]

A. play  

B. played

C. would play  

D. was going to play

中国和墨西哥是世界上薯蓣资源最丰富的国家，产量各占世界市场份额的三分之一。我国年产皂素约（）t左右，出口120多个国家和地区，出口量居世界第二。