What is the name for the ability of living things to maintain a relatively constant internal environment? homeostasis stimulus-response cellular respiration metabolism?

The answer should be homeostasis.

Examples of homeoststais in human, the ability to maintain a constant internal environment includes maintaining body temperature, where we would shiver when cold so that our muscles can move and respire so heat is generated, or we sweat when hot, so that our body can cool down. Another example includes maintaining a constant blood glucose concentration, if our blood glucose is too high, insulin (a hormone) is secreted, or if it's too low, another hormone called glucagon is secreted.

On the other hand, all of the other choices are not the right answer. Stimulus response is where we respond to certain stimulus, where nerve cells are involved. For example, we pull our hand away if we touch hot stuff. Respiration is just the exchange of oxygen and glucose to carbon dioxide and water to produce energy. It is how the cells generate energy. And metabolism is just generally the chemical reactions within our body.

Therefore your answer is homeostasis.

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.