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, (c1, c2) - c1.getPopulationO- c2.getPopulationO);
b. Arrays. sort (countries, compare(ci -> c1.getPopulationO, c2- c2.getPopulation()) :J
c. Arrays. sortCcountries, c -c. getPopulation());
d. Arrays. sort(countries, comparator(c - c. getPopulationo)))