The most famous conductor of the underground railroad sang "go down moses" as the code message , it was time to go, was john rankin
jane lewis
harriet tubman
elijah anderson

Aor d are either one of the answers to that.

True blindness may be caused by trauma to the eye, severe conjunctivitis due to  ibr (infectious bovine rhinoceros) or pink eye or other infections, leptospirosis, lead poisoning, selenium toxicity, fungal infections, vitamin a  deficiencies, rabies, vitamin b12 deficiency, neoplastic of the orbit or  conjunctiva, cataracts, congenital malformations, etc. 

Exposition riding action. climax. falling action. denouement