When Asked About His Vision, a Patient Says That the Last

When asked about his vision, a patient says that the last time he had it tested, his vision was recorded as 20/50.What does this mean?

A) He can read at 20 feet what a person with normal vision can read at 50 feet.
B) He can read at 50 feet what a person with normal vision can read at 20 feet.
C) He needs to be 50 feet from objects to see them.
D) He can see objects the best between 20 and 50 feet.