Among the options given, the best example of an asset is a) the necklace someone is wearing. An asset is typically defined as anything of value or a resource owned by an individual or entity that is expected to provide future economic benefits.
The necklace has intrinsic value; it can be sold or used as collateral, thereby fulfilling the criteria of an asset. In contrast, the electricity in a home (b) is a service that provides immediate consumption rather than ownership, making it a utility expense rather than an asset. The coffee someone drank this morning (c) has no residual value and cannot be converted into cash, hence not qualifying as an asset. An old used airline ticket (d) also generally holds nominal value, as it is typically non-transferable and has likely expired, thus lacking any present economic benefit.