Question

Researchers have found clear and convincing evidence ________ happiness is the key to better health and longer lives.

A．where

B．whether

C．how

D．that

Answer 1

D

解析试题分析：考查同位语从句。从句部分“happiness is the key to better health and longer lives”是主系表结构，不缺少成分，evidence证据、fact事实、question问题、doubt疑问、idea想法等词，后面常跟that引导的同位语从句，来对名词进行补充说明。句意：研究人员已经发现清晰、有说服力的证据，开心是健康和长寿的关键。故选D。
考点：考查同位语从句