Because green house air is like carbon dioxide and is toxic for people to breathe in but they want to put it under an act that says it will cause u no harm
The correct answer is letter A. Venom glands and varied diets are the reasons why cane toads are considered as invasive species in Australia. They cause major ecological imbalance within their immediate surroundings and have caused an infestation all over Australia.
I'm not exactly sure what specifically you are asking for in relationship to balancing equations, but I have some examples with working out so you can examine them and try to go through the steps with them.
Hope this helps! <3