请教：Prep I DS 3道题目

Ｍａｔｈ一直不好。。ＪＪ和prep一起联系。。。

3. 196-!-item-!-187;#058&000141

How many different prime numbers are factors of the positive integer n ?

(1) Four different prime numbers are factors of 2n.

(2) Four different prime numbers are factors of n2.

答案选Ｂ，我选Ｄ

根据１，Ｎ应该除２以外有３个prime factors  不知哪里想错了

23. 1653-!-item-!-187;#058&000843

At least 100 students at a certain high school study Japanese. If 4 percent of the students at the school who study French also study Japanese, do more students at the school study French than Japanese?

(1) 16 students at the school study both French and Japanese.

(2) 10 percent of the students at the school who study Japanese also study French.

答案B   我选D

16/ 4%=400>100

40. 3636-!-item-!-187;#058&003488

Beth's bank charges a service fee on a regular checking account for each month in which the balance on the account falls below $100 at any time during the month. Did the bank charge a service fee on Beth's regular checking account last month?

(1) During last month, a total of $1,000 was withdrawn from Beth's regular checking account

答案E，我选C； 这题完全不明白为什么会是E，难道题目同时考虑存钱的因素？

23题我跟你选项一样，我也选了D,我再次看了一下题目，我猜想问题是否出在at least?

是否说至少100个学生学习日语，但是并没有说究竟几个啊，所以虽然通过16个学生可以确定法语的学习人数，但是因为日语人数不确定，所以A还是没法确定