Q1:

If the current in the given circuit is increased to 24 mA, the source voltage must have tripled.

ANS:B - False

Obviously, if we change the resistance to 100 ohms instead of 300 we increase the circuit current by a factor of 3. This question is flawed!

We have to assume that the resistance is not subject to change as defined in the circuit diagram.
The supply voltage, however, must be assumed to be the only value subject to change as it does not have a definitive value to begin with.

If you answered TRUE to this question whilst taking into account that the resistor value is fixed and not subject to change, in my opinion, it is correct, well done!