Which among the following is a haloarene?

Maximum bond angle is present in

Which part of the human brain controls the breathing movements?

The principle of immunization or vaccination is based on the property of ..........

Two radioactive materials $X_1$ and $X_2$ have decay constants $10\lambda$ and $\lambda$ respectively. If initially they have the same number of nuclei,then the ratio of the number of nuclei of $X_1$ to that of $X_2$ will be $1/e$ after a time:

If a chord of the parabola $y^2=4x$ passes through its focus and makes an angle $\theta$ with the $X$-axis,then its length is