For several decades now, amphibian species worldwide have been in decline. A significant proportion of the decline seems to be due to the spread of the chytrid fungus Batrachochytrium dendrobatidis (Bd). Chytrid sporangia reside within the epidermal cells of infected animals, animals that consequently show areas of sloughed skin. Infected animals can also be lethargic, which is expressed through failure to hide and failure to flee. The infection cycle typically takes four to five days, at the end of which zoospores are released from sporangia into the environment. Zoospores are spores of fungi (as well as some algae and protozoans) that use a flagella for swimming locomotion. In some amphibian species, mortality rates approach 100%; other species seem able to survive the infection. The fact that infection by Bd causes lethargy in many infected amphibians can have what effect on efforts to accurately census the numbers of dead or dying amphibians at a particular time, in a particular habitat?
I. It can cause underestimation due to infected amphibians preferring to seek out refuges relative to uninfected amphibians.
II. It can cause underestimation due to increased predation on, and removal of, infected amphibians relative to uninfected amphibians.
III. It can cause overestimation because infected frogs should be more readily observable to human census-takers than should uninfected amphibians.

a. I and II
b. I, II, and III
c. II and III
d. II only