In an experiment of verification of Ohm’s Law, following observations are obtained: 

Potential difference V (in volt)	0.5	1.0	1.5	2.0	2.5
Current I (in ampere)	0.2	0.4	0.6	0.8	1

What will be current I when the potential difference V is 0.75 V? 

Using the Ohm's Law, questions involving such data are easily resolved. The current flowing through a conductor between two places is precisely proportional to the voltage across the two points, or $P=IR$, according to Ohm's Law.
Equation used:
Ohm's Law, or $V=IR$, will be the formula we employ to answer the question.
The conductor's resistance may be determined from the observation that was just made.
Let R be the resistance.
Ohm's Law tells us that
$V=IR$
Now you can get the data from each column in the watch table to find the value of R.
For example, let us take $V=0.5V$and$I=0.2A$
So,
$R=\frac{V}{I}$
$R={\displaystyle \frac{0.5}{0.2}}={\displaystyle \frac{5}{2}}$
$R=2.5\mathrm{\Omega }$
To find the current when the potential difference $V=0.75V$:
Again, using Ohm’s Law
$V=IR$
$⟹I={\displaystyle \frac{V}{R}}$
$I=\frac{0.75}{2.5}=0.3A$
$I=0.3A$
Therefore, if the potential difference is 0.75 V, the current  through the conductor 
will be 0.3 A.

Hence, the correct answer is option B.