The Development of Artillery in Late-Medieval Europe Affected Military Strategy

The development of artillery in late-medieval Europe affected military strategy in that:

A) foot soldiers were no longer useful on the battlefield.
B) mounted knights became more useful on the battlefield.
C) stone castles became less viable as defensive strongholds.
D) national monarchies could no longer control rebellious aristocrats.
E) monasteries could now defend themselves as well as any town.