What electric field strength is needed between the electrodes to achieve this deflection?

The electric field produces a force that is found between two charges which are similar to that of the gravitational force found between masses. The perpendicular lines that you can see in your diagram represent the electric field between two electrodes.

It is d, all the other ones say incorrect answer .

The best answer is (a) which is universal law is in effect at all times. it is constantly at play in everything we do and governs our lives. it is also important to note that universal law applies to not only everything on earth, but everything in the universe as well, which is another reason why it is in effect at all times.