A leaf electroscope is a simple apparatus to detect any charge on a body. It consist of two metal leaves OA and OB, free to rotate about O. Initially both are very slighty separted. When a charged object is touched to the metal knob at the top of the conduction re, charge flows from knob to the top of the conduction rod, charge flows from knob to the leaves through the conducting rod, charge flows from knob to the leaves through the conduction rod. As the leaves are now charged similarly, they start repelling each other and tet separted (deflected by certain angle).

The angle of deflection in static equilibrium is an indicator of the amount of charge on the charged boy.
When `a+20C` rod is touched to the knob, the deflection of leaves was `5^(@)`, and when an identical rod of `-40C` is touched, the deflection was found to be `9^(@)`. If an identical rod of `+30C` is touched, then the deflection may be:

Options

A. 0
B. `2^(@)`
C. `7^(@)`
D. `11^(@)`

Answer

C