[单选题]
2. Which factor is a /j)7scggn5s tcause of thena0o-5qicu+sqjn oh2k8- w f+ change in Boreal forests from net carbon accumulation to netnq 5uj 0o+-si+-awqkhco 8n2f loss?
A. Increased photosynthesis.
B. More frequent forest fires.
C. Increased respiration in trees.
D. Afforestation.
