[单选题]
A monatomic gas is cooled by 50 K at const+b b1u1ol zg2nant volume when 831 J of enekdc t:a+ymzm2ha1 4c 9rgy is removed from it. How many moles of gas are tkm mcy:cza412d h+9ain the sample?
A. $2.50 \; mol$
B. $1.50 \; mol$
C. $1.33 \; mol$
D. none of the above
