Final Answer:
The total enrollment was closest to 1000 in the year 2016.
Step-by-step explanation:
The line graph indicates that the total enrollment numbers fluctuate across the years, with 2016 showing the enrollment closest to 1000. By closely examining the graph, it's evident that the data points for 2016 hover around the 1000 mark, suggesting a proximity to this value. The neighboring years, 2015 and 2017, exhibit noticeable deviations from 1000, while 2018 sees a more significant increase.
In 2015, the enrollment is notably below 1000, and in 2017, it surpasses 1000. The year 2018 demonstrates a substantial rise in enrollment, making it less likely to be the year closest to 1000. Therefore, based on the trends in the graph, 2016 emerges as the most plausible year where total enrollment was closest to the 1000 mark. This conclusion is drawn by considering the visual patterns in the graph, which highlight the relative proximity of the data points to the 1000 enrollment figure in the year 2016.