Put s for subordinate clauses, and i for independent clauses.
1. we had an enjoyable weekend when we spent two days on lloyd's farm.

we had an enjoyable weekend is underlined

2. before the sun came up, we had eaten a huge breakfast.

before the sun came up is underlined

3. jeremy milk several cows, and tamara spread grain for the chickens.

tamara spread grain for the chickens is underlined

4. i slowly drove the tractor to the barn, but steven attached the tractor's trailer.
steven attached the tractor's trailer is underlined

5. after we loaded the trailer with bales of hay, we hauled the load into the pasture.

after we loaded the trailer with bales of hay is underlined

6. i wasn't afraid of the cows until one of them lumbered toward me.

until one of them lumbered toward me is underline

1. I: Independent Clause - We had an enjoyable weekend contains a subject (We) and a verb (had). It does not contain any conjunctions that would make it necessary to include more information.

2. S: Subordinate Clause - Before the sun came up contains the subordinating conjunction "before" which transitions between the idea of the sun coming up and eating a huge breakfast.

3. I: Independent Clause - Tamara spread grain for the chickens is a complete idea. It is joined to another complete idea using a comma and a conjunction (and). The subject is Tamara and the verb is spread.

4. I: Independent Clause. Steven attached the tractor's trailer is a complete idea joined to another complete idea using a comma and a conjunction (but). Steven is the subject and attached is the verb.

5. S: Subordinate Clause - After is the subordinating conjunction that transitions from loading the trailer to hauling it to the pasture.

6. S: Subordinating clause. Until is the subordinating conjuction that transitions from not being afraid to being afraid when the cow gets closer.

Letter c is the answer.