问题
Researchers have found clear and convincing evidence ________ happiness isthe key to better health and longer lives.
A:where
B:whether
C:how
D:that
B:whether
C:how
D:that
正确答案是：
同类题型
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Must I hand in my homework now， Mr.Smith?—No，you ________.
It’s raining outside. Would you please ______me your raincoat?—Sure, here you are.