The answer would be: <span>a. cooler temperatures
</span>Increase in distance from the equator will reduce the amount of sunlight received, which will make the area have a cooler temperature. I<span>ncrease in elevation above sea level should make the air pressure lower as there is less air above the area.</span>
<span>Commensalism is an interaction in which one of those species would benefit, and the other one would not be affected. Parasitism is an interaction in which one of those species would benefit at the expense of the host organism. Thus, in commensalism we have one positive and one neutral result while in parasitism we have one positive and one negative result.</span>
Both. You can use it as singular or plural.