It's now pretty well established that apreviously unstudied fungus (Batrachochytrium dendrobatidis—batrachos is Greek for "froga-or Bd for short) is responsible for the mass extinction of so many frogs. Why hadn't it killed them all before? a. The frogs are more biologically vulnerable because of changes in their skin
b. Radioactive fallout made it more deadly
c. It mutated
d. Boats and planes weren't around​