[单选题]
A container of an idurspux/wt x*:2ad)g yv ,g0u-eal gwufa m( m11 qo3tm*o )uyt2ctf4e; lz:as at 1 atm is compressed to one-third its volume, with the temperature held constant. What is its final ao)u*lm1 ftefym2 wm(1;3uttczqo4: pressure?
A. $1/3 \; atm$
B. $1 \; atm$
C. $3 \; atm$
D. $9 \; atm$
