What is the meaning of "contrivances"?

The term "contrivances" refers specifically to devices or gadgets that are designed or created, often with a particular purpose in mind. It suggests not just physical objects but also mechanical or innovative creations that allow for solutions to problems or enhancing functions. This definition aligns well with the concept of devices and gadgets, which are tangible items crafted to perform specific tasks or functions.

The other choices provide meanings that do not accurately capture the essence of "contrivances." For example, while a complex problem might involve the need for a contrivance, it does not define what the term itself means. Similarly, plans that backfire and unintentional acts do not relate to the notion of devices or mechanical inventions, which is the core of what contrivances encompass. Therefore, the most fitting definition among the options is that of devices or gadgets.