[单选题]
A container of an ideale jc10 uzdf4wz6v/iq6 g,wqzq ucb e+)5as at 1 atm is compressed to one-third its volume, with the temperature held constant. What is i)q, zwb q5c+euts final pressure?
A. $1/3 \; atm$
B. $1 \; atm$
C. $3 \; atm$
D. $9 \; atm$