Male citizens are only required to serve in the draft if called up

a. at least 21 years old
b. there is a war or national emergency
c. they do not register with the selective service
d. no women are serving

There is a war or national emergency (B)

mark other guy brainliest

ww1 weapons: tank. tanks were used for the first time in the first world war at the battle of the somme. they were developed to cope with the conditions on the western front. the first tank was called 'little willie' and needed a crew of 3.