21 F(n) is defined as the product of all even numbers from 2 to n, inclusive. What is the least prime factor of f(100) + 1.

　　A. From 2 to 10

　　B. From 10 to 20

　　C. From 20 to 30

　　D. From 30 to 40

　　E. Greater than 40

22 If point (a, b) is on line k, is the distance from the point to origin greater than 5?

　　(1) a – b > 5

　　(2) a^2 + b^2 > 5

23 Is m/n > n/m?

　　(1) m > n

　　(2) mn > 0

24 How many intersection does y = x^4 – x^2 have with x--‐axis?

　　A. 0

　　B. 1

　　C. 2

　　D. 3

　　E. 4

25 Is x > 0?

　　(1) x^2 – x^3 = 0

　　(2) |x| = x

答案：

21. E

22. B

23. C

24. D

25. E