A flask filled with water and organic molecules was left open to the air for an hour and then was tightly stoppered. After being allowed to sit for a week, the flask was reopened and checked for living organisms. Only anaerobic bacteria were found living in it. Which of the following can be assumed about the conditions within the flask during the week it sat tightly stoppered? A. There was no oxygen in the flask.
B. There were carbon-based gases in the water.
C. There was abundant oxygen in the flask.
D. Sunlight must have entered the water.