(a)- Rat; (b)- Dog, (c)- Tortoise, (d)- Crow
(a)- Dog; (b)- Squirrel, (c)- Bat, (d)- Deer
(a)- Squirrel; (b)- Cat; (c)- Rat, (d)- Pigeon
(a)- Deer; (b)- Rabbit; (c)- Frog, (d)- Rat
The provided text gives multiple possible answers for the organisms at positions (a), (b), (c), and (d) in a food web. Without the food web image, it's impossible to definitively determine the correct answer. Each option presents a different combination of organisms. To solve this, the food web diagram is required to ascertain the trophic levels and relationships among the organisms listed.