Read the following excerpt from Joseph Stalin's radio broadcast on July 3, 1941: We must strengthen the Red Army's rear, subordinating all our work to this cause,all our industries must be got to work with greater intensity to produce more rifles, machine-guns, artillery, bullets, shells, airplanes; we must organize the guarding of factories, power stations, telephonic and telegraphic communications, and arrange effective air-raid protection in all localities. which of the following is the most likely the meaning of "subordinating"

a) Fighting to survive in a difficult circumstances
b) Joining with others to achieve a common goal
c) Placing in a lower or less important position
d) achieving with an increased effort or energy