Climbing Mount Everest great skills and not without risk.
A. requires；are
B. required；were
C. requires；was
D. requires；is
网友回答
A. requires；are
B. required；were
C. requires；was
(答案→)D. requires；is
解析：说明客观事实用一般现在时。Climbing Mount Everest动名词作主语，谓语动词用第三人称单数。