Q36:

If a and b are positive integers such that a – b and  are both even integers, which of the following must be an odd integer?

A.   

B.    

C.    

D.   

E.    

Answer: D

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Q37:

During a trip, Francine traveled x percent of the total distance at an average speed of 40 miles per hour and the rest of the distance at an average speed of 60 miles per hour.  In terms of x, what was Francine’s average speed for the entire trip?

A.   

B.    

C.    

D.   

E.    

Answ E

请问各位大侠为什么？