The first food chain, "Grass→Sheep→Wolf" is in the right order.
B is incorrect because it jumps from algae to shark, when plankton should be in the middle.
C is incorrect because it starts with the rabbit instead of grass.
D makes sense but is still incorrect because it's backwards. Food chains are meant to start from the bottom and work all the way up. Meaning a food chain should generally start with some sort of plant and end with the biggest animal/predator.