It came as a great to the parents that their son finally came back safe and sound.A. fav

问题补充：

It came as a great to the parents that their son finally came back safe and sound.

A. favor

B. sense

C. relaxation

D. relief

答案：

A. favor

B. sense

C. relaxation

(答案→)D. relief

解析：A. favor恩惠，帮助，B. sense感觉，C. relaxation放松，D. relief 宽慰，缓解，根据句意：儿子安然无恙的回来对父母是个安慰。所以选D。