If a three-digit number is selected at random from the integers 100 to 999, inclusive, what is the probability that the first digit and the last digit of the integer will both be exactly two less than the middle digit?
100到999中首位数字=末位数字=第二位数字-2的数字有131，242，353，464，575,686，797，有7种可能，故本题选B项。