Which one of the following elements on doping with germanium,makes it a $p$-type semiconductor?

The basis of the quantum mechanical model of an atom is

Which of the following is a Lewis acid?

The position vector of a point lying on the line joining the points whose position vectors are $\hat{i}+\hat{j}-\hat{k}$ and $\hat{i}-\hat{j}+\hat{k}$ is:

The term independent of $x$ in the expansion of $\left(\sqrt{x}-\frac{2}{\sqrt{x}}\right)^{18}$ is

$A$ driver applies the brakes on seeing the red traffic signal $400 ~m$ ahead. At the time of applying the brakes,the vehicle was moving with $15 ~m/s$ and retarding at $0.3 ~m/s^2$. The distance covered by the vehicle from the traffic light $1$ minute after the application of brakes is (in $~m$)