问题
选择题
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
答案：D
同位语从句考查题。 研究者发现清晰、具有说服力的证据当提及健康长寿的生活时幸福是关键。 中心词是evidence连接词that在从句中只起连接作用不做成分，选D。