求助一道prep的数学题

solojj

Last month 15 homes were sold in Town X.  The average (arithmetic mean) sale price of
the homes was $150,000 and the median sale price was $130,000.  Which of the following statements must be
true?

    

  I  At least one of the homes was sold for more than
$165,000

    

I I  At least one of
the homes was sold for more than 130,000 and less than$ 150,000

    

 I I I   At least one
of the homes was sold for less than $130,000

    

(A) I only

    

(B) II only

    

(C) III only

    

(D) I and II

    

(E) I and III

    

  选A

为什么？我有点头发胀了