Answer:
The answer is (b). q large and m small.
Explanation:
We know that whenever a charged particle having charge '[tex]q[/tex]' is moving with a velocity '[tex]v[/tex]' through an electric field ([tex]\overrightarrow{E}[/tex]) and a magnetic field ([tex]\overrightarrow{B}[/tex]), it will experience a force, called Lorentz Force ([tex]F_{L}[/tex]), given by
[tex]\overrightarrow{F_{L}} = q(\overrightarrow{E} + \overrightarrow{v} \times \overrightarrow{B} )[/tex]
Now, due to this Lorentz force if the charge having mass '[tex]m[/tex]' gains an acceleration '[tex]a[/tex]', then
[tex]&&ma = q(\overrightarrow{E} + \overrightarrow{v} \times \overrightarrow{B})\\&or,& a = \frac{q}{m}(\overrightarrow{E} + \overrightarrow{v} \times \overrightarrow{B})[/tex]
The deviation of the particle will be maximum when the acceleration of the article is maximum. Therefore to obtain the best possible resolution, according to above equation, '[tex]q[/tex]' has to be large and '[tex]m[/tex]' has to be small.