The population is going to decline. The reason it will decline is because of the word 'pressure' which signifies that there is a struggle for survival. If a population is struggling to survive, this means that there is either too many secondary consumers (not enough tertiary consumers to eat the secondary consumers), or the primary consumers are reproducing enough.
Food chain goes as follows:
Primary Producer - Grass
Primary Consumer - Grasshopper
Secondary Consumer - Rat
Tertiary Consumer - Snake
Quaternary Consumer - Hawk
