The tedium was occasionally relieved by a large-scale search-and-destroy operation, but the exhilaration of riding the lead helicopter into a landing zone was usually followed by more of the same hot walking, with the mud sucking at our boots and the sun thudding against our helmets while an invisible enemy shot at us from distant tree lines.
a. the paradox in the excerpt illustrates the idea that
b. danger could alleviate the monotony of war.
c. walking was often necessary after flying.
d. the soldiers could not see their enemies.
e. the heat was more difficult to overcome than the enemy