Now one of the most serious problems many people are worried about _____ on the lack of adequate housing space
A.insists
B.depends
C.agrees
D.focuses
网友回答
D解析考查动词：这些动词都可以和on搭配，
A. insists坚持，
B. depends 依赖
C. agrees同意
D. focuses专注，句意：现在很多人担心的最严重的问题重点在房屋空间缺少上。选D。