The correct answer is A. Bombing a city kills lots of innocent civilians, bombing a military target doesn't
Strategic Bombing is a way of a bombing that is designed to destroy a country’s ability to wage war by demoralizing civilians and targeting features of an enemy’s infrastructure.
At the beginning of WWII all nations maintained a policy of only attacking military targets only, this avoided the killing of civilians. But the German Luftwaffe began bombing British cities, like London. This was used to demoralize the population and force the surrender of the UK - what did not happen -.