Why Did the Miller‒Urey Hot Chemistry Experiment Exclude Oxygen in Its

Multiple Choice

Why did the Miller‒Urey hot chemistry experiment exclude oxygen in its investigation of the chemical origin of life on Earth?

A) Oxygen is not necessary for life.
B) The scientists assumed the reactions would produce oxygen from water vapor.
C) The scientists assumed that photosynthetic organisms would develop in the apparatus.
D) There is no evidence that oxygen existed in Earth's earliest environments.
E) The scientists wanted to avoid contamination of the apparatus by oxygen-consuming bacteria.