Over the past two decades, the popularity of the bicycle as a mean of transportation and recreation has increased tremendously in the United States.

【正确答案】 1、正确答案：mean--means

【答案解析】解析：考查名词辨析。mean作名词，表示“中间；平均数”，用于此不符合句意。此处表示“方法，手段，工具”，应该用以s结尾的名词means。