OEQuote:
Well, 0 is not prime, and neither is 1, which leaves 4 prime number possibilities of the 9 total. Since the spins are independent events, multiply the chances of the prime numbers together:4/9*4/9*4/9=16/81
Of course the other answer choices represent what happens if you miscount primes or add instead of multiply. Evil! (Although if you really just had to guess, you could at least eliminate E as being greater than the maximum probability of 1.)