6 letters have to be put into their 6 respective envelopes. If the letters are inserted randomly into the envelopes, what is the probability that all the letters go into their respective envelopes?
Choose the correct option:	A) 1/720	B) 1/60	C) 1/120	D) 1/240	E) 3/5
A-B-C-D-E (envelopes)   a-b-c-d-e (letters)   6 letters (a, b, c, d, and e) can be assigned to 6 envelopes (arranged) in 6! ways, out of which only one will be correct, thus the probability is 1/6! = 1/720.   1/720nswer: 1/720
<result>A</result>
6 letters have to be put into their 6 respective envelopes. If the letters are inserted randomly into the envelopes, what is the probability that all the letters go into their respective envelopes?