Answer:
3. rolling a sum of 20 with two standard dice
Explanation:
If something has a probability of 0 then there is no chance of it happening
A standard die goes up to 6. The max sum you can get by rolling two dice would be 12 as 6 + 6 = 12. So you have no chance of rolling a sum of 20 with two standard dice therefore the probability would be 0.