【正确答案】 C

【答案解析】[解析] pollute：污染、弄脏，例如： The violent films pollute the minds of the young men．暴力电影毒害着青年人的思想。widen：加宽、变宽，例如：The gap between income and expenditure has widened to 11%．收入和支出之间的差额已扩大到11%。blacken：使变黑，例如：The soldier blackened his face with charcoal．那名士兵用木炭把他的脸涂黑。mix：混合、使混合，例如：The painter was busy mixing his colours．画家在忙着调颜色。