In the context of shock, which of the following can cause severe infections?

Severe infections can result from exposure to pathogens, which is the correct choice in this context. Pathogens, such as bacteria, viruses, fungi, and parasites, are microorganisms that can enter the body and lead to infections, especially when the immune system is already compromised, such as in cases of shock. Shock can reduce blood flow and the delivery of oxygen and nutrients to tissues, weakening the body's overall defenses and making it more susceptible to infections.

The other options do not directly relate to causing severe infections. While the body adapting is a normal physiological response, it does not inherently cause infections. Similarly, low physical activity wouldn't directly lead to infections; although regular physical activity supports immune function, inactivity alone doesn't expose the body to pathogens. A normal hormonal balance is important for maintaining various bodily functions, including the immune response, but it does not cause infections per se.