2. 下列计算正确的是································································································ （ ）
A．7a＋a＝7a 2 B．5y－3y＝2 C．3x2y－2yx2＝x2y D．3a＋2b＝5ab
3. 在－1，1.2，|－2|，0，+（－2），（－1）2014中，负数的个数有··························· （ ）
A．2个 B．3个 C．4个 D．5个
4. 今年国庆期间全国首次实行免收7座及以下小型客车公路通行费，据交通部门统计，免费首日全国道路旅客运输量共完成85 600 000人，则该人数用科学计数法表示应为···················································· （ ）
A．85.6×106 B．856×105 C．8.56×107 D．8.56×108
