It is not until the disease has progressed to AIDS a person begins to look sick.
A. who
B. that
C. where
D. before
网友回答
A. who
(答案→)B. that
C. where
D. before
解析：考查强调句型。本题强调的是时间状语从句not until the disease has progressed to AIDS。句意：直到这个病发展为艾滋病的时候，这个人看起来才很虚弱。故B正确。