If E and F are independent events associated with an experiment, then which one of the following statements is correct?

A committee of 4 students is selected at random from a group consisting of 8 girls and 4 boys. Given that there is at least one boy in the committee, the probability that there are exactly 2 boys in the committee is

The probability distribution of the random variable X is given by

The variance of the random variable X is

Urn I contains 6 red balls and 4 black balls and Urn II contains 4 red balls and 6 black balls. One ball is drawn at random from Urn I and placed in Urn II. If one ball is drawn at random from Urn II, then the probability that it is a red ball is :

Let box I contains 3 black and 4 white balls, box II contains 2 black and 2 white balls, box III contains 4 black and 3 white balls. A box is selected at random and then a ball is randomly drawn from the selected box. If the color of the ball is black then the probability that the ball is drawn from box III, is:

Bag A contains 2 red and 3 white balls, Bag B contains 3 red and 2 white balls. If a ball is drawn at random and is found to be red, then the probability that it was drawn from bag B, is :

The standard deviation of the number of tails in three tosses of a coin is: