C. The solar system formed from space dust, after all.
Explanation:
The topic sentence is:
Space exploration is not a waste of money.
We'd expect this passage to follow up on why investing in space exploration <em>is</em> a good use of money.
Here are the sentences that follow:
Rocket companies and astronaut training programs give high-paying jobs to skilled professionals.
The technologies they create helps people on earth daily.
This tells us that skilled space professionists are well-paid because the technologies they create help us daily. This is related to how space exploration is worth investing in.
The solar system formed from space dust, after all.
This sentence has no relation whatsoever to our topic. It does not relate back to the topic sentence.
