The correct answer is: C. is rising
The population of the world is currently increasing at a rate of about 1.1% per year. This means that the world’s population is expected to double in about 69 years. The main reason for this rapid population growth is that the number of births is still higher than the number of deaths.
Option A, “rise”, is incorrect because it is in the past tense. The population of the world is not rising, it is is rising.
Option B, “rises”, is incorrect because it is in the present tense. The population of the world is not rises, it is rising.
Option D, “rose”, is incorrect because it is in the past tense. The population of the world is not rose, it is rising.