1选择题
The pencil is about 15 _______ long.
答案：B
解析：本题考查长度单位的选择。铅笔的长度通常用厘米(cm)来表示，毫米(mm)太小，米(m)和千米(km)太大。易错点是学生可能混淆不同长度单位的适用场景。
2选择题
A school bus can carry about 2 _______ of weight.
- A. grams
- B. kilograms
- C. tons
- D. meters
答案：C
解析：本题考查重量单位的选择。校车的承载重量通常用吨(tons)来表示，克(grams)和千克(kilograms)太小，米(meters)是长度单位。易错点是学生可能对大型物体的重量单位缺乏概念。
3填空题
Tom has 15 apples. He gives 7 to his sister. He has _______ apples left.
答案：8
解析：本题考查万以内的减法（退位）。15 - 7 = 8。易错点是学生可能在退位计算时出错，或忘记写单位（但本题题干已明确单位，答案只需填数字）。
4填空题
There are 24 hours in a day. 3 p.m. is _______ in 24-hour clock time.
答案：15:00
解析：本题考查24时计时法。下午3时等于15时。易错点是学生可能忘记将下午时间加上12。
5解答题
Sarah has 3 boxes. Each box has 24 stickers. How many stickers does she have in all?
答案：3 × 24 = 72 (stickers). Sarah has 72 stickers in all.
解析：本题考查多位数乘一位数（进位）。3 × 24 = 72。易错点是学生在计算 3 × 4 = 12，进位后计算 3 × 2 = 6，再加进位1时可能出错。
6解答题
A rectangle has a length of 8 cm and a width of 5 cm. What is its perimeter?
答案：Perimeter = (8 + 5) × 2 = 13 × 2 = 26 (cm). The perimeter is 26 cm.
解析：本题考查长方形周长的计算。公式为（长+宽）×2。易错点是学生可能忘记乘以2，或者将长和宽相加后直接作为答案。
7解答题
There are 12 students in a group. 4 of them are girls. What fraction of the group are girls?
答案：The fraction of girls is 4/12, which can be simplified to 1/3.
解析：本题考查分数的初步认识。女孩占总人数的 4/12，约分后为 1/3。易错点是学生可能直接写 4/12 而忘记约分，或者将分子分母写反。
8解答题
Lily is 6 times as old as her little brother. Her little brother is 2 years old. How old is Lily?
答案：Lily's age = 6 × 2 = 12 (years old). Lily is 12 years old.
解析：本题考查倍的认识。莉莉的年龄是弟弟的6倍，即 6 × 2 = 12 岁。易错点是学生可能误用除法（12 ÷ 2 = 6）或加法（2 + 6 = 8）。