<span>The answer is A. A stable ecological niche leads to the absence of selection pressures, which in turn causes species to remain unmodified or in stasis. This can be simplified with an example: If there are just enough lions on an island and just enough buck for both species to survive without the lions starving or the buck being killed off, neither of the species would have to adapt to survive because their predator-prey relationship is stable. This means that they can continue to live in this state of stasis or equilibrium. </span>
Respiration uses oxygen to make CO2, which goes back into photosynthesis to make oxygen. The end products of each basically cycle back into each other.
The sentence, from the choices given, that contains the correct subject-verb agreement is; Books and television entertain us on a rainy day. The correct answer will be A.
