According to a UN report a third of the world population have no to clean drinking water

问题补充：

According to a UN report, a third of the world population have no to clean drinking water and health care．

A. means

B. approach

C. channel

D. access

答案：

A. means

B. approach

C. channel

(答案→)D. access

解析：have access to得到；利用。