[单选题]As environmental pollution is threatening human beings as a whole, it’ s high time countries throughout the world（ ）the problem on a global scale.
A
considered
B
consider
C
are considering
D
have considered
正确答案：A
题目解析
本题考查虚拟语气。
句意：由于环境污染正威胁着整个人类，所以世界各国应该在全球范围内考虑这个问题。
由题干可知是It’s high time that引导的虚拟语气，表示“是某人该做某事的时候了”。从句谓语要用一般过去时或“should＋动词原形”其中should不能省略。故A选项符合题意。
