Which of the following statements correctly provides a comparator function using lambda expressions to sort an array of countries by population, assuming the existence of a getpopulation method? a. arrays. sort(countries, comparator(c -> c.; b. arrays. sort(countries, compare(c1 -> c1. c2 -> c2.; c. arrays. sort(countries, (c1, c2) -> c1.getpopulation() - c2.; d. arrays. sort(countries, c -> c.;