Final answer:
Option A). The distance a train travels as a function of time is a continuous function, while the number of children born as a function of years is a discrete function.
Step-by-step explanation:
The question asks which options are examples of continuous functions. A continuous function is one where the values change smoothly without jumps or breaks in the domain.
a) The distance a train travels as a function of time is indeed a continuous function because distance changes continuously as time progresses. There is no point in time where the train travels a certain distance, and then suddenly, without a fractional interim, travels a different distance.
b) The number of children born as a function of years is actually a discrete function because the number of children can only be whole numbers, and there is a clear jump from one integer to the next.
Therefore, the correct answer is: a) The distance a train travels as a function of time.