False: Heart disease and Most Cancers are not viruses. Or at least as far as I know. However complicating the issue is the fact that after a viral infection, heart disease can develop.
Cancer is another example, and the answer again is not black and white. 16% of all cancers can trace their beginnings to a bacteria or virus. That leaves 84% whose beginnings are not that clear.
The question is not black and white. I'd be careful how you think of it. If something is a complication, is that a direct cause? I still think the answer is false, but don't be surprised if your instructor disagrees. Move on to something a little less black and white.
Volcanoes can be constructive if they happen in the ocean, as they can form islands and therefore be new places for plants and animals to grow and thrive.
Volcanoes can be destructive if they kill a large amount of animals by forming on land.
