Final answer:
Shakespeare primarily earned most of his income through writing and selling plays and also invested in real estate.
Step-by-step explanation:
Shakespeare primarily earned most of his income through writing and selling plays. He was a playwright and a part-owner of the acting company, the Lord Chamberlain's Men, which later became the King's Men. In addition to writing, Shakespeare also acted in his own plays.
Shakespeare also invested a significant portion of his wealth in real estate purchases in Stratford. He bought the second-largest house in town, New Place, in 1597. In his final years, he had become prosperous and well-known.
Therefore, the correct answer is A) Writing and selling plays.