The correct answer is C. Must have at least 3 trials.
The binomial distribution is a probability distribution that describes the number of successes in a sequence of independent experiments each of which yields success with probability $p$. The binomial distribution is often used to model the number of successes in a sequence of Bernoulli trials.
The conditions for the binomial distribution are:
- The number of trials must be fixed.
- The trials must be independent.
- The probability of success must be constant for each trial.
- The number of successes must be a whole number.
The condition that the number of trials must be fixed is not met in option C. The binomial distribution can be used to model a sequence of trials with any number of trials, including 3 or less.
The other options are all conditions of the binomial distribution.
Option A states that there are only 2 possible outcomes. This is true for the binomial distribution, which is a discrete probability distribution. Discrete probability distributions only have a finite number of possible outcomes.
Option B states that the probability of success must be constant for each trial. This is also true for the binomial distribution. The probability of success is a parameter of the binomial distribution, and it is assumed to be constant for all trials.
Option D states that the trials must be independent. This means that the outcome of one trial does not affect the outcome of any other trial. This is also a condition of the binomial distribution. The independence of trials is assumed in the binomial distribution.