Knowing how to think clearly and how to speak correctly one confidence.
A. give
B. has given
C. have given
D. gives
网友回答
A. give
B. has given
C. have given
(答案→)D. gives
解析：考查主谓一致：句意：知道怎么清楚地思考怎么正确的说话给人自信。Knowing how to think clearly and to speak correctly这一个整体在句子中是充当主语成分的动名词，谓语用单数，排除AC，因为这是客观事实，用一般现在时，选D。