$A$ complex of platinum,ammonia,and chloride produces four ions per molecule in the solution. The structure consistent with this observation is:

The coordination number of a metal crystallizing in a hexagonal close-packed structure is

The cubic equation whose roots are thrice to each of the roots of $x^3+2 x^2-4 x+1=0$ is

$\int \frac{dx}{(x+1) \sqrt{4x+3}}$ is equal to

Match the following and find the correct pairs.

List $I$	List $II$
$(A)$ Fleming's left hand rule	$(i)$ Direction of induced current
$(B)$ Right hand thumb rule	(ii) Magnitude and direction of magnetic induction
$(C)$ Biot-Savart law	(iii) Direction of force due to magnetic induction
$(D)$ Fleming's right hand rule	(iv) Direction of magnetic lines due to current

An object takes $n$ times as much time to slide down a $45^{\circ}$ rough inclined plane as it takes to slide down a perfectly smooth inclined plane of the same inclination. The coefficient of kinetic friction between the object and the rough incline is given by: