We have to categorize the events based on the likelihood of their occurrence.
An event with a probability between 0.5 and 1 is likely, while an event with a probability between 0 and 0.5 is unlikely.
The first event is "picking a dime randomly from a piggy bank containing 18 dimes, 3 nickels and 2 pennies".
As the majority of the coins are dimes (18 out of 23 coins), the probability of picking a dime is high and the event is very likely to happen.
The probability is actually P = 18/23 ≈ 0.783.
The second event is "picking a brown puppy randomly from a litter with 4 white puppies, 1 brown puppy and 1 black puppy".
In this case, the probability is 1 out of 6, which is approximately 0.167. Then, this event is unlikely.
The third event is "picking a mango randomly from a bowl that holds 15 mangoes, 3 apples and 2 bananas".
This is the same case as the dimes: the mangoes are majority in the bowl, so the probability of picking one is expected to be higher than 0.5. Then, this event is likely.
The fourth event is "picking a pink ribbon randomly from a box containing 4 pink, 12 red and 4 white ribbons".
In this case, the pink ribbons are not majority and the probability of picking one is less than 0.5. Then, the event is unlikely.
We can summarize as: