Which one of the following is the most widely accepted method of contraception in India,as at present?

To which series does $Catharanthus$ $roseus$ belong?

The figure shows a system of logic gates. From the study of the truth table,it can be found that to produce a high output $(1)$ at $R$,we must have

In the arrangement shown in the figure,the masses of blocks $B$ and $A$ are $2m$ and $m$ respectively. The surface between $B$ and the floor is smooth. Block $B$ is connected to block $C$ by means of a string-pulley system. If the whole system is released,find the minimum value of the mass of block $C$ so that block $A$ remains stationary with respect to $B$. The coefficient of friction between $A$ and $B$ is $\mu$.

An oxide of an element is a gas and dissolves in water to give an acidic solution. The element belongs to

Which of the following is the most primitive ancestor of humans?