Final answer:
The amplitude of the population oscillation is 50, calculated by taking the difference between the highest value (550) and the lowest value (450) and dividing by two.
Step-by-step explanation:
The amplitude of an oscillation is defined as the measure of its change over a single period. This is calculated as half the distance between the highest value and the lowest value of the oscillation. In the case of a population oscillation between a high of 550 and a low of 450, the amplitude would be the difference between the peak and the trough divided by two.
So, the amplitude = (High - Low) / 2 = (550 - 450) / 2 = 100 / 2 = 50.
Hence, the correct answer is a. 50.