Which factor indicates the amount of charge on the source charge?
a. the number of field lines on the test charge
b. the number of field lines on the source charge
c. the direction of lines on the source charge
d. the direction of lines on the test charge

B. the number of field lines on the source charge

Explanation:

As we know that electric flux is defined as the number of electric field lines passing through a given area.

So here  electric flux due to a point charge "q" is given by

so here we know that flux depends on the magnitude of charge and hence we can say that number of filed lines originating from a point charge will depends on the magnitude of the charge.

so here correct answer will be

B.   the number of field lines on the source charge

tube or goog with be a great resource to with that question

be subject to a force andchange its motion