Which of the following acids is a vitamin?

In the circuit shown in the figure,the $AC$ source gives a voltage $V = 20 \cos (2000 t)$. Neglecting source resistance,the voltmeter and ammeter readings will be:

If $f: R \rightarrow R$ is defined by $f(x)=[2x]-2[x]$ for $x \in R$,where $[x]$ is the greatest integer function,then the range of $f$ is:

The equation of the sphere passing through the points $(1,0,0)$,$(0,1,0)$,and $(1,1,1)$ and having the smallest radius is:

When a $p-n$ diode is reverse biased,then

The distance between the lines represented by $4x^2 + 20xy + 25y^2 + 2x + 5y - 12 = 0$ is equal to