John, a Colorado resident, tried cannabis once and decided he didn't like the way it made him feel. He didn't use it again. A month later, he received a job offer to teach in an elementary school in North Dakota, pending a clear drug screening. John's drug screening was positive for THC and his job offer was rescinded. Why?
A It can take several months for THC to leave to the body
B Even though cannabis is legal in CO, it is not legal federally.
C John must have been exposed to second-hand cannabis smoke after his first try for his screening to be positive.
D Both A and B.
E All of the above.