Oxygen!
Plants release carbon dioxide, oxygen, and water vapor through their stomata. Oxygen is less needed because water and carbon dioxide can be changed into sugar.
An example of serious poaching problems is the diminishing population of Tigers.
For example in India, this has severely affected the survival-probability of tigers. There were 20000 Tigers in India in the 20th century, and now there are only 3000. This shows the severity of the problem. The government is now taking serious steps against the poachers.
The answer is B, they were not overlapping in range, so they evolved and became not identical.
