Answer:
The digestive system works very closely with the circulatory system to get the absorbed nutrients distributed through your body. ... While the digestive system collects and removes undigested solids, the excretory system filters compounds from the blood stream and collects them in urine.
Biologically thinking, I would say viruses.
Viruses are Inert organisms, they are not influenced by temperature on the opposite of other organisms like humans or bacteria (there are some exceptions in bacteria)
Temperature influences proteins, it could change their conformation and their activity, especially for enzymes.
Temperature decreases the energy flow, due to the decrease of thermal agitation of small molecules like ions in cells.
Viruses don't need active enzymes to live, it just needs host cells, which will be easier on cold days because of the decrease of immune system activity
On cold days you can see an emergence of viruses infections like flu or cold.
Activational effect is the correct answer.
Activational effect is an impermanent hormonal effect that leads to a change in physiological activity or behavior in both humans and adult animals. For instance, when testosterone levels rise in male songbirds they become more aggressive and tend to engage in courtship behavior. Also, a pregnant woman may get more emotional than usual due to an extra level of progesterone and estrogen during pregnancy.
