A dependent clause is a group of words with a subject and a verb, but doesn't make much sense on its own. A lot of times, especially in a sentence with a comma, you can split the sentence and see if it makes any sense.
6. "Before we hiked"
7. "When we go on nature field trips."
8. "Since John was an expert of volcanoes"
9. "If you want to see something closer."
10. "After a volcano erupts"
None of those answers make sense as independent sentences, which is how you can tell they're dependent clauses; they depend on the other part of the sentence.
(D) because "an apprentice" is singular, so it should have singular pronouns. "Their" should be "his or her."
The sieve filters the sand and you get resources out of it.
