The answer would be A, as B refers to conduction and C and D refer to radiation. Convection is the transfer of different temperature currents, i.e, A
The force applied to the cannonball and cannon is equal. The explosion inside the cannon will generate a pressure which will turn into a force on both cannonball and cannon. The cannon being heavier and fixed to the ground will move a bit, but the cannonball will be thrown away, fired.
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1 degree Celsius.
P = V^2 / R.
So, 3.3^2 / 0.025 = 435.6W.
Note, you can get the power equation from:
P = V*I. Also, I = V/R.
Substituting V/R in for I in the 1st equation, you get P = V^2 / R.
