Which of the following is a branch of biology?

Assertion $(A)$: Cyclohexane is the most stable cycloalkane.
Reason $(R)$: Cyclopropane and cyclobutane are less stable due to angle strain and torsional strain.
The correct answer is:

The angle between the tangents drawn from the point $(1,4)$ to the parabola $y^2=4x$ is

$A$ straight line which makes equal intercepts on positive $X$ and $Y$ axes and which is at a distance of $1$ unit from the origin intersects the straight line $y = 2x + 3 + \sqrt{2}$ at $(x_0, y_0)$. Then $2x_0 + y_0$ is equal to

The period of $\left(\tan \theta - \frac{1}{3} \tan^3 \theta\right) \left(\frac{1}{3} - \tan^2 \theta\right)^{-1}$,where $\tan^2 \theta \neq \frac{1}{3}$,is

The half-life of a radioactive element is $10 \ h$. The fraction of initial radioactivity of the element that will remain after $40 \ h$ is