During world war i, which already existing weapon was made significantly more effective with new technology?
a. poisonous gas
b. trench
c. machine gun***
d. submarine

i think c, can someone check my answer? !

During World War I, Machine gun, already existed weapon was made significantly more effective with newer technology.

Option C

Machine gun was a famous and popular weapon during World War I where the death toll of soldiers and injuries was recorded in millions. In the beginning these weapons were hand cracked but with high demand and technology they were improved to automatic weapons which fired about 450-600 bullets per minute.

New methods of firing were also developed during the battle. One country responsible for improving machine gun was Germany creating machine gun sharpshooter which helped their troops to with attacking formation.

254.34

step-by-step explanation:

the formula for area of a circle is given by

a = pi * r^2

a = pi * 9^2

a = 81*pi

using 3.14 as an approximation for pi

a = 3.14*81

a = 254.34