In the Reptile House at a zoo you will probably find a case (11)_____ of small tree frogs. Now, a great (12)_____ of creatures like to eat frogs, and so some frogs as a (13)_____ can ooze out a substance on their skin (14)_____ makes them taste horrible. These frogs are generally banded (15)_____ bright warning colours, like orange, red, yellow and bright green. This, of course, makes them (16)_____ like brightly-coloured sweets, and rather good to (17)_____ but the birds and animals in the forest have learnt (18)_____ bitter experience that these frogs are the (19)_____ that tastes the worst, and so they leave them (20)_____.
A.creature
B.thing
C.example
D.warning