They do not have external ears like us. but they do have ear holes located directly behind their eyes. frogs ear holes are covered with thin tympanic membranes or the eardrums that protect the inner ear cavity.
Let me try...
How about, grass, moose(moose eats grass), black fly(when moose dies it's eaten by fly), fish(fish can catch flies sometimes), and then Osprey(birds eat fish).
The second one... How about, grass, deer(deer eats grass), then wolf(eats deer), the mosquito(sucks wolf's blood), I don't know the dragon fly though
HOPE THAT HELPED SOMEWHAT :)
A,b I think should be the answer