C

In a grassland ecosystem, the trophic levels and their respective examples are as follows:
First Trophic Level: This level consists of producers which are typically plants. In this case, it is Grass.
Second Trophic Level: This level consists of herbivores that feed on producers. In this case, the example is Rabbit.
Third Trophic Level: This level consists of primary consumers or carnivores that feed on herbivores. Here, it is Crow.
Fourth Trophic Level: This level includes higher-level carnivores that consume other carnivores. The example given is Vulture.
Therefore, the correct matches are: (A-iv), (B-iii), (C-i), (D-ii), which corresponds to Option C.