Consider the following:

1. Butterflies

2. Fish

3. Frogs

How many of the above have poisonous species among them?

The correct option is All three.

To understand why this is correct, we can look at the presence of poisonous species in each of the three groups listed:
1. Butterflies: Several species of butterflies are poisonous to predators. A classic example is the Monarch butterfly (Danaus plexippus). During their larval stage, Monarch caterpillars feed on milkweed plants, which contain toxic cardiac glycosides. The caterpillars sequester these toxins and retain them through metamorphosis, making the adult butterflies poisonous to birds and other predators.
2. Fish: There are many species of poisonous fish. A notable example is the Pufferfish (family Tetraodontidae), which contains tetrodotoxin, a highly potent neurotoxin found in its internal organs (like the liver and ovaries) and sometimes skin. Pufferfish are considered among the most poisonous vertebrates in the world.
3. Frogs: The most famous examples of poisonous frogs are the Poison Dart Frogs (family Dendrobatidae) native to Central and South America. These brightly colored frogs secrete lipophilic alkaloid toxins through their skin, which serve as a chemical defense mechanism against predators.

Since all three groups (Butterflies, Fish, and Frogs) contain species that are poisonous, the correct answer is indeed "All three".