[讨论]请教几道PREP的数学~！！！谢谢~~

For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive.  If p is the smallest prime factor of h(100) + 1, then p is

(E) greater than 40

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The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present.  If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

(A) 100% decrease

(B) 50% decrease

(C) 40% decrease

(D) 40% increase

(E) 50% increase

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In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best.  If each song was selected 4 times, how many students were surveyed?

(A) 96

(B) 48

(C) 32

(D) 24

(E) 18

A certain stock exchange designates each stock with a one-, two-, or three-letter code, where each letter is selected from the
                26 letters of the alphabet.  If the letters may be repeated and if the same letters used in a different order constitute a different code, how many different stocks is it possible to uniquely designate with these codes?

 (E)  18,278