Challenge: Al, Bob, Cal and Don each own 1 hat. If the 4...

Probability (no one receives his own hat) = numbers of outcomes in which no one receives his own hat ;
Let Al's hat = a , Bob's hat = b, Cal's hat = c, Don = d
For Al = b, c, d
Bob = a, c, d
Cal = a, b, c
The 4 of them can pick up 3 different hats. 3 time without receiving their own hat hence outcome for not receiving own hat = 9 Outcome (3 hats * 3 times)
Given that we can arrange the 4 hats in 4 different ways ;
a, b, c, d
b, c, d, a
c, d, a, b
d, a, c, b Total number of outcomes = 4 (!) ways
$$=4!=4\cdot3\cdot2\cdot1=24ways\ or\ possible\ outcomes$$
Probability (no ones receives his own hat) $$=\frac{9}{24}=\frac{3}{8}$$
$$answer\ is\ option\ D$$