His ability has never been in doubt----the question is ___________ or not he is prepared to work hard.

A．that

B．if

C．where

D．whether

西江经济带要突出（）作用，重点加强与珠三角的产业对接，深度参与区域产业分工。

A、货源富集

B、黄金水道

C、通道和纽带

D、沟通粤港澳