The researchers found clear and convincing evidence _________ happiness is the k

题型：不详难度：来源：

The researchers found clear and convincing evidence _________ happiness is the key when it comes to better health and longer lives.

A．where

B．whether

C．how

D．that

答案

D

解析

试题分析：句意：研究人员发现清楚的令人信服的证据当说到健康和长寿的时候，快乐是关键。这里是that连接同位语从句，说明evidence的内容，选D。