The correct answer is B. 50.
The base resistor method is a technique used to calculate the collector current in a transistor. The collector current is equal to the base current multiplied by the beta (β) of the transistor. Beta is a measure of the current gain of the transistor, and it is typically in the range of 50 to 200.
If the value of β changes by 50, then the collector current will change by a factor of 50. This is because the collector current is proportional to β.
For example, if the base current is 1 mA and the β is 100, then the collector current will be 100 mA. If the β changes to 150, then the collector current will be 150 mA.
The base resistor method is a simple and accurate way to calculate the collector current in a transistor. It is often used in transistor circuits, such as amplifiers and oscillators.
The other options are incorrect because they do not take into account the effect of β on the collector current.