What does it mean to "apply" something?

To "apply" something typically means to actively use, place, or implement it in a specific context. In the context of the correct choice, this definition aligns with actions like placing a substance onto a surface (such as applying paint), putting on an article of clothing (like applying a coat), or spreading a treatment (such as applying medicine). This involves a direct engagement and utilization of items or concepts in practical situations, demonstrating their intended function or benefit.

The other choices reflect various forms of inactivity or removal, which do not encapsulate the essence of application. Disregarding or rejecting something suggests a lack of use, while removing entirely indicates a complete withdrawal rather than engagement. Observing without action implies a passive stance, which also deviates from the concept of applying, where one takes an active role in using or instituting something. Thus, the correct choice accurately embodies the meaning of application in both a literal and figurative sense.