[单选题]
2. Which factor is a m dcyt+ z /forp54*s zs;std48n )bso)+ a5)cflvs1r vcause of the change in Boreal forests from net carbon accumulation to n5 fscl+v vr1a)et loss?
A. Increased photosynthesis.
B. More frequent forest fires.
C. Increased respiration in trees.
D. Afforestation.
