Which of the following compounds on oxidation gives methyl ethyl ketone?

All of the following substances react with water. Which pair among them will produce the same gaseous product upon reaction with water?

Which of the following is true for organisms of the same species?

The differential equation of all circles which pass through the origin and whose centres lie on the $Y$-axis is

The mean of a set of observations is $\bar{x}$. If each observation is divided by $\alpha$ $(\alpha \neq 0)$ and then increased by $10$,what is the mean of the new set?

If the circle $x^2+y^2+8x-4y+c=0$ touches the circle $x^2+y^2+2x+4y-11=0$ externally and cuts the circle $x^2+y^2-6x+8y+k=0$ orthogonally,then $k=$