Because you cannot test it or observe it.
A scientific theory are created through the scientific method, in the scientific method you need to be able observe it and experiment.
The appropriate answer is c. global warming. Global warming is an increase in the global temperature caused by the increased use of fossil fuels. Using fossil fuels since the industrial revolution has pumped extra carbon dioxide in the atmosphere than what would actually enter from natural processes. This extra carbon dioxide is increasing the green house effect and causing the temperature to increase.
Answer:
Cell membrane
Explanation:
Sumer has come up with a great analogy for a presentation she is giving in her psychology class. The membrane encasing a neuron only allows some ions to pass in and out of its channels. And she is going to describe this cell membrane as a guard only allowing some patrons to enter and leave a controlled area.