Final answer:
The global population is expected to increase significantly by 2050 despite the slowing down of the human population growth rate.
Step-by-step explanation:
The question pertains to global population trends and the expectations for population size by the year 2050. Given the current trends and projections by experts, such as those from the United Nations, although the rate of human population growth is indeed slowing down, the global population is still expected to increase significantly by 2050. Thus, the answer to the student's question would be option (a) Increase significantly. It is important to note that while growth rates are expected to decline, they remain positive, meaning that more people will continue to be born than the number of people dying, thus still driving an overall increase in the population size