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

In a family having three children,there may be no girl,one girl,two girls,or three girls. So,the probability of each is $\frac{1}{4}$. Is this correct? Justify your answer.

In a packet containing $400$ screws,$120$ screws are defective. $A$ screw is picked up randomly from the packet. Then,the probability that the screw picked up is non-defective is .........

$I$ toss three coins together. The possible outcomes are no heads,$1$ head,$2$ heads and $3$ heads. So,$I$ say that probability of no heads is $\frac{1}{4}$. What is wrong with this conclusion?

There are $1000$ sealed envelopes in a box,$10$ of them contain a cash prize of $Rs. 100$ each,$100$ of them contain a cash prize of $Rs. 50$ each,$200$ of them contain a cash prize of $Rs. 10$ each,and the rest do not contain any cash prize. If they are well shuffled and an envelope is picked out,what is the probability that it contains no cash prize?

$A$ carton contains $100$ trousers of which $73$ are good,$12$ have minor defects and $15$ have major defects. Manu rejects only those trousers which have major defects. One trouser is selected at random from the carton. Then,the probability that the selected trouser is accepted by Manu is $\ldots \ldots \ldots \ldots .$