without friends the most difficult challenge for Chuck while living on the island.
A. How to survive, is
B. How does he survive, are
C. How does he survive, is
D. How to survive, are
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(答案→)A. How to survive, is
B. How does he survive, are
C. How does he survive, is
D. How to survive, are
解析：考查主谓一致。句意：当库克住在岛上的时候没有朋友怎样生存对他来说是最难的挑战。排除B和D，是因为无论是动词不定式还是从句做主语时谓语动词都用单数，，C不对是因为C语序不对，因为从句做主语时是陈述语序，所以A是动词不定式做主语谓语动词用单数，所以A正确。