Solving a few math probability problems although they are multiple choice but I hope you write the steps clearly my exercise book has only the answers but not the steps.

3. There are 4^3=64 kinds of total ****

The maximum value is 2 indicating that the method of distribution is (2,1,0,0) and since 0 is repeated once, there are 4!/2=12 kinds

12/64=3/16, choose D

4. There are 10 combinations of 10 choices of 6 in the total ****,***10**9*8*7*6*5/6/6/5/4 /3/2/1=210 kinds

If we designate 4 seats to be filled, we first seat these 4 seats and then assign them, so it is 6 pick 2 combinations, 6*5/2/1=15 kinds

So the probability is 15/210=1/14, choose B

5. The total number is 9*10^6

The kinds without 0 are 9^7, the 9-free The variety is 8*9^6, and the probability that both of them do not contain is 8^7, so choose E

Looking for the adoption, thanks