_____ we were worried about was _____ they could manage to control the pollution.

A：where

B：what  

C：which

D：that

A：whose  

B：which  

C：what

D：that

A：Anyone

B：The one  

C：Whoever

D：Who

A：when

B：that

C：how

D：what

A：what  

B：who  

C：that  

D：as

A：when

B：where  

C：which

D：what

A：It

B：What

C：As

D：Which

A：that

B：which

C：what

D：how

A：whichever

B：however

C：whatever  

D：whoever

A：Anyone gambles

B：No matter who gambles

C：Whoever gambles

D：Those gamble