[单选题]
2. Which factor is a cause of the change inkzy0b+i 3n(i e Boreal/gl-2q ncba9 l84s mta,cq4 yh forests from net carbon accumulation to net lo ,smlq lbq4 y h-at48acnc9g/2ss?
A. Increased photosynthesis.
B. More frequent forest fires.
C. Increased respiration in trees.
D. Afforestation.
