What sociological perspective stresses that age has no inherent meaning, and that each culture shapes the way its citizens perceive the elderly?

The answer is "symbolic interactionism".

The symbolic interaction perspective, additionally called symbolic interactionism, is a noteworthy structure of sociological theory. This viewpoint depends on the representative implying that individuals create and depend upon during the time spent social cooperation. Albeit representative interactionism follows its inceptions to Max Weber's statement that people demonstration as indicated by their elucidation of the importance of their reality, the American logician George Herbert Mead acquainted this viewpoint with American human science in the 1920s.

i think it is the third one.