The correct answer is B: there will be more adults. In their forecasts, the UN experts calculate that just 1 percent of the population increase will come from 0.37 billion more children(age 0 to 14).
69 percent from 2.5 billion more adults (age 15 to 74).
And 30 percent from 1.1 billion more very old people (age 75 and older). The data comes from UN Population statistics.