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
考查同位语从句。that解释前面的名词evidence，证据就是快乐是关键当谈到身体更健康寿命更长的时候。所以选D。