Please help I need to get an answer.

General conditions necessary for natural selection to occur are:

More organisms are born than can survive.

Organisms vary in their characteristics, even within a species.

Variation is inherited.

Differences in reproduction and survival are due to variation among organisms.

So, it would be the last option.

Hope this helps! (:

1. when the tempature rises,your sweat glands and then springs into action making perspiration. some sweat evaporates with your skin taling heat with it.2.some of the blood pumped by the heart travels by your lungs to get rid of carbon dioxide and pick up oxygen.3.saliva produces by, you drinking water which saliva is 98% of. when mucus builds up in your body it also creates saliva as well as, antibacterial compunds.4.when the core body tempature drops, the shivering reflex is triggered to maintain homeostasis. for example: when you get out the pool you start to shiver because it is cold.