Final answer:
The word that means 'lasting only a very short time; fleeting' is 'transient.' This term describes situations or states that are short-term and is opposite in meaning to 'tangible,' which refers to something that can be touched or is concrete.
Step-by-step explanation:
The question asks for a word that means 'lasting only a very short time; fleeting.' From the given options, option B, transient, best matches this definition. Transient refers to something that is temporary or not lasting. It is a term often used to describe situations or states that are short-term and subject to change. This contrasts with tangible, which refers to something that can be touched or is concrete, not necessarily related to the duration of time something lasts.
Comparatively, 'tangible' would not accurately describe something of short duration. It is generally used to refer to physical objects that are perceptible by touch. Hence, for a word that describes a fleeting existence, 'transient' is the appropriate adjective.