单选题 Looming over the debate about human interference in the world's boreal forests is an as yet unanswerable question: Will the effects of global warming eventually dwarf man's impact?

A、 raise to greater importance
B、 make more difficult to measure
C、 cause to appear small
D、 bring to an abrupt end

【正确答案】 C

【答案解析】后面一句的句意：全球变暖的后果会最终使人类的影响力变小吗? dwarf(使)变矮小；cause to appear small使……看起来小；raise to greater importance重要性上升；make more difficult to measure使……更难衡量；bring to an abrupt end草草收场。