A carbon film resistor has coloured code Green Black Violet Gold. The value of the resistor is:
(A) $50M\Omega $
(B) $500M\Omega $
(C) $500 \pm 5\% M\Omega $
(D) $500 \pm 10\% M\Omega $

Hint: The values of resistors are given by colour codes, where each value of resistor are given by a separate colour code. The tolerance of resistors are also given by different colours. The sequence of colours corresponding to different values can be remembered by the following letters: BB ROY OF GREAT BRITAIN HAS VERY GOOD WIFE, where each letter corresponds to a specific colour.

Complete Step-By-Step Solution:
We know that a variety of resistors are available in the market each having different values. The magnitude of resistance can be understood by looking at the particular resistor.
Thus, the tolerance and the value of the resistor is printed on the body of the resistance itself.
The bands of colour which represent the value of resistance and its tolerance are known as resistance colour codes.
The colour codes are read from left to right, and the rightmost band having the largest width reads tolerance.
Using the phrase: BB ROY OF GREAT BRITAIN HAS VERY GOOD WIFE, where each letter corresponds to a specific colour respectively: Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey and White.
The numbers are marked from 0 to 9. The digits are placed side by side depending on the order in which the colour band occurs.
The tolerance is depicted by two colours Silver and Gold, where Silver denotes $10\% $tolerance and Gold denotes $5\% $.
The last band from left corresponds to tolerance and the second last band corresponds to the multiplying factor.
 Therefore, in the given question, seeing the colours gin we obtain magnitude of resistance is
$R = 50 \times {10^7} \pm 5\% $

This is the required value of resistance and thus, option (C ) is correct.

Note:
Tolerance of resistor indicates the change in value of resistance that can be expected. That is the obtained value can be less or greater than the original value up to the limit of tolerance value. At times, another band indicating the temperature coefficient is also present.