Answer:
max2(max2(population1,population2),max2(population3,population4));
Explanation:
This expression will give the maximum form the population1,population2,population3,population4.Since max2 can only accept two integer variables.So we have to use nested max2 function.I have used 3 max2 functions.One max2 finds the maximum from population1 and population2 second max2 finds the maximum from population3 and population4 and the last max2 finds the maximum from the results of first max2 and second max2.