If an event cannot occur,then its probability is

The probability of any event cannot be ..........

Two balanced dice are rolled. Find the probability that the sum of numbers on two dice is odd.

There are $5$ white, $7$ red, $4$ black, and $2$ blue identical balls in a box. One ball is selected at random from the box. Find the probability that the ball is red.

Two balanced dice are rolled. Find the probability that the sum of numbers on two dice is smaller than $7$.

The probability of the month of April in any year having $5$ Sundays is ......... (in $/7$)