The correct options are
A High demand led to deforestation.
B Charcoal was too fragile to be transported over long distance.
D Charcoal was too delicate and any form of impurities affected the purity of iron.
Charcoal was produced by burning trees in the forests. With extensive deforestation, the forest area got reduced. Charcoal was fragile, and transporting it to long distances was a difficult process. It sometimes had impurities, due to which it could not generate high temperatures, resulting in the production of low-quality iron.