ANSWER
Step-by-step explanation
The probability of any event is a positive number between 0 and 1.
Let E be a subset of S. The probability of event E ocurring is defined as the ratio of the number of elements in E to the number of elements in S.
Since E is a subset of S, E always has less elements than S or the same number of elements. Hence, its probability has to lie between 0 and 1.
On the other hand, the probability is a ratio between two amounts. Amounts are positive numbers. Therefore, the division between two positive numbers is another positive number.