For a,w,d are the positive integers, and d|a means that “a is divisible by d”, if d|aw, which of the following must be true?
Choose the correct option:
A) d|a B) d|w C) d|2aw D) d|(a+w) E) d|(a-w)
d/a means a is divisible by d   d/aw means ab divisible by d.   all are integers so ,   if aw is divisible by d,   1 a can be divisible by d   or   2 w can be divisble by d.   so the question stem asks must true.   so option a and b are could but not must.   option c is 2aw divisible by d. if ab is divisible by d then 2aw is divisible by d.   option d and e we can't predict.   so option d|2aw is correct.
<result>C</result>
For a,w,d are the positive integers, and d|a means that “a is divisible by d”, if d|aw, which of the following must be true?