C because you need to order it from fastest to slowest and the least amount of time taken is the fastest.
Answer:

Explanation:
Given that:
- magnetic field intensity,

- kinetic energy of electron,

- we have mass of electron,

<em>Now, form the mathematical expression of Kinetic Energy:</em>




<u>from the relation of magnetic and centripetal forces we have the radius as:</u>



No. You cannot rule out the battery even after the open circuit voltage measurement. The open-circuit voltage may not have changed but the battery's internal resistance may have greatly increased.
It is round or say spherical to widen the range of photography and it is designed to focus the image as the ray are coming from infinity so !!
I am not an expert of camera but ya it is the main theme !!