Consider the following :1.Butterflies2.Fish3.FrogsHow many of the above have poisonous species among them ?

1. A

   Only one

   Only one. Poisonous butterflies, fish and frogs all exist.

2. B

   Only two

   Only two. Under-counts.

3. C

   All three

   All three. Monarchs and others; puffer/stonefish; poison-dart and some Indian frogs.

4. D

   None

   None. Each group has toxic species.

Summary. Official key is (c) all three. Some butterflies sequester plant toxins. Many fish are venomous or poisonous (puffer, stonefish). Frogs include poison-dart species and other toxic amphibians. So butterflies, fish and frogs all have poisonous species.