单选题 One of the aims of the organization is to develop and encourage recycling practices that are ______ economically viable and environmentally sound.

A、 both
B、 if so
C、 as
D、 not only

【正确答案】 A

【答案解析】[解析] 语法：连词固定搭配
1．空格后出现连词and，很自然联想到both A and B，因此A．both为正确选项。
2．注意以下固定搭配：both A and B，neither A nor B，not only A but also B。