Final answer:
To find the probability, multiply the percentage of college students majoring in STEM fields by the percentage of STEM majors who believe people could live on Mars. The answer is 28%.
Step-by-step explanation:
To find the probability that a randomly selected college student believes that people could live on Mars in the future, we need to consider the two probabilities given. First, we know that 40% of college students major in STEM fields. Second, among those STEM majors, 70% believe that people could live on Mars in the future.
To find the probability we are looking for, we multiply these two probabilities together:
Probability = (40%)(70%) = 28%
Therefore, the answer is a) 28%.