Which of the following uses $RNA$ as a template strand for $DNA$ synthesis?

At $27^{\circ} C$,$500 \ mL$ of helium diffuses in $30 \ minutes$. What is the time (in hours) taken for $1000 \ mL$ of $SO_2$ to diffuse under the same experimental conditions?

For an ellipse with eccentricity $e = \frac{1}{2}$,the centre is at the origin. If one directrix is $x = 4$,then the equation of the ellipse is

If $X = \{ 4^n - 3n - 1 : n \in N \}$ and $Y = \{ 9(n - 1) : n \in N \}$,then $X \cup Y$ is equal to

The functional kidney of a frog tadpole is:

Assertion $(A)$: Ductile metals are used to prepare thin wires.
Reason $(R)$: In the stress-strain curve of ductile metals, the length between the points representing elastic limit and breaking point is very small.