单选题 The suggested causes of a given phenomenon cannot always be independently observed, and so it is hard to ______ the possibility of there being explanations alternative to the one proposed.
A．account for B．rule out C．guard against D．do with

【正确答案】 B

【答案解析】[解析] B选项rule out(排除……)符合题意。A选项account for的意思是“解释”；C选项guard against的意思是“防备”；D选项do with可以用have be to do with sth．，意思是“与某事有关”，都与题意不符。本题空格处是说很难排除其他一些可能的解释。因此B选项为正确答案。