Why do you suppose many adults pine for the “good old days,” either an earlier era in history or their own youthful high school/college days? Is this generally a harmless or harmful thing? Why?

Maybe that was the peak of their existence. The time at which they'd accomplished most things, when they'd met the greatest people, when they'd fallen in love and fallen out.

It is harmless as long as they do not live in the past. Reminiscence is not a bad thing. But they have to remember to live in the present.

However, it's not the same for all adults.

Not everyone has had an eventful youth. For some, 'the time of their life' arrive at a later point. For others, it doesn't happen at all.

the service industry in the united states grew in the late 1800s. what was one effect of that growth?

the number of people with jobs in factories as unskilled workers decreased.

the number of people with jobs in factories as unskilled workers increased.

the middle class grew as people took jobs as clerks, lawyers, and teachers.

the middle class shrank as people left jobs as clerks, lawyers, and teachers.

c. "but thy eternal summer shall not fade" (line 9)