What principle states that a sterile object remains sterile only when it is touched by other sterile objects?

The principle outlined in the correct answer emphasizes the critical importance of maintaining sterility in clinical and laboratory settings. When a sterile object is only touched by other sterile objects, it can remain free from contamination, as any contact with non-sterile items introduces a risk of microbial transfer. This principle is foundational in procedures like surgeries or when handling sterile instruments and materials, ensuring that the integrity of sterility is upheld throughout the process.

In contrast, the other options do not fully capture this essential aspect of sterility. Contamination by touch implies a more general idea about the transfer of germs but lacks the specificity that defines the relationship needed to maintain sterility. The visibility of a sterile field refers to the need to keep sterile areas clear and unobstructed but does not explain the fundamental principle of touch and sterility. Lastly, while clean hands are crucial in preventing contamination, this statement does not encompass the broader principle regarding the interaction of sterile items with each other. Hence, the first option best encapsulates the essential concept of maintaining sterility through controlled contact.