Which river is the longest river in the V. K. that rises in the mountains of Wales

A．there is a definite relationship between high levels of lead and death.
B．the patients with brain tumors have higher levels of lead in their bones.
C．some workers have higher risks of developing brain cancers than others.
D．higher levels of lead have a long-term effect on children over a lifetime.

A．He constantly opened up wasteland.
B．His way of living was rather primitive.
C．He was eager to grow trees and crops.
D．He was not heard to utter a single word.