The probability of getting head and tail alternately in three throws of a coin (or a throw of three coins) is:

$A$ die has two faces each with number $1$,three faces each with number $2$,and one face with number $3$. If the die is rolled once,determine $P(2)$.

$A$ card is selected from a pack of $52$ cards. How many points are there in the sample space?

From a well-shuffled pack of cards,one card is drawn at random. The probability that the card drawn is an ace is

If $A, B,$ and $C$ can hit a target $4$ out of $5$ times,$3$ out of $4$ times,and $2$ out of $3$ times respectively,what is the probability that exactly two of them hit the target?

If $A, B$ and $C$ are mutually exclusive and exhaustive events of a random experiment such that $P(B) = \frac{3}{2} P(A)$ and $P(C) = \frac{1}{2} P(B)$, then $P(A \cup C)$ equals to