The author lost his sight due to an infection in his eye, caused by strain and prolonged focus. The correct answer is option B.
The author of "Experience: 1 First Saw My Wife 10 Years After We Married" lost his sight due to an infection in his eye, not being blind from birth (A), a reaction to medicine (C), or being injured in a car accident (D).
In the passage, the author mentioned that his vision became impaired after continuously copying by a dim window for a few weeks. This suggests that the strain on his eyes from the dim light and prolonged focus may have led to an infection, causing the loss of his sight.
Therefore, the correct answer is B. He got an infection in his eye.