[单选题]
A person tries to heat up her nokgfg-du9i /p o.;t 2b)l.ht:+u8jqoam9p . x9t jgzkath water by adding 5.0 L of water at $80 \; ^{\circ}C$ to 60 L of water at $30 \; ^{\circ}C$. What is the final temperature of the water?
A. $34 \; ^{\circ}C$
B. $36 \; ^{\circ}C$
C. $38 \; ^{\circ}C$
D. $40 \; ^{\circ}C$
