Which of the following forces causes comets to regularly return to the inner solar system after being gone for many years?

The answer is GRAVITY.

I just did it on Study Island. :)

the exclusive possession or control of the supply or trade in a commodity or service.

answer: in 1900, there were no "workplace safety laws"!

explanation: at the beginning of this century, workers in the united states faced remarkably high health and safety risks on the job.

a century ago in 1900 about three hundred out of every one hundred thousand miners were killed on the job each year.

[industria] developments occurred within a legal and regulatory climate that diminished employer’s interest in safety. as a result, americans developed production methods that were both highly productive and often very dangerous.