Which of the following is true?
a. Bats serve as a reservoir for Ebola, but do not themselves get the disease.
b. Bats serve as a reservoir for Ebola, frequently living with low-grade symptoms of the disease.
c. Bats suffer the effects of Ebola, then transmit it to humans while they themselves are still alive.
d. Bats transmit Ebola to people only after they themselves are dead.