最小的两位数与最大的一位数之和是(      )。

家庭制作酸奶的主要步骤有：①新鲜的全脂（或脱脂）乳和糖混合；②冷却（42～45℃）；③热处理（煮沸）；④发酵（放在室内温暖的地方数小时）；⑤接种（加入一些购买的酸奶）；⑥冷藏或食用．以下按操作的先后顺序排列的是（　　）

一辆汽车在平直公路上匀速行驶，下列与其相关的各对力中，属于平衡力的是（   ）

如下数表是由从1开始的连续自然数组成，观察规律并完成各题的解答．

    Today is Friday. Peter has six classes today. He goes to school at 7:30 a.m. At 8:00 a.m., he begins his first class. The first class is English. At 9:00 a.m., he has math. Peter likes math because it’s interesting. At 10:00 a.m. she has a biology class. Peter thinks it's very boring. Then at 11:00 a.m., he has a history class. That's his favorite subject. He can learn a lot about the past from history.
    Peter has lunch at school at about 12:00. Then he has a short break. At 1:30 p.m., he has a music class. At 2:30 p.m., he has a P.E. class. Peter likes this afternoon, because music and P.E. are easy and interesting. School is over at 4:00 p.m. Peter is happy because he can go home and have a good time on Saturday and Sunday.
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