$A$ person can kill a bird with a probability of $3/4$. He tries $5$ times. What is the probability that he may not kill the bird at all?

$A$ multiple-choice examination consists of $5$ questions. Each question has $3$ alternative answers,of which only $1$ is correct. What is the probability that a student will get $4$ or more correct answers?

If the standard deviation of the random variable $X$ is $\sqrt{3pq}$ and the mean is $3p$,then $E(X^2) = . . . . . . .$

If $8$ coins are tossed simultaneously,what is the probability of getting at least $6$ heads?

$A$ multiple choice examination has $5$ questions. Each question has three alternative answers of which exactly one is correct. The probability that a student will get $4$ or more correct answers just by guessing is:

If $8$ coins are tossed simultaneously,then the probability of getting at least $6$ heads is