Lucio is revising his written response in social studies. What error did he make in the sentence below? "Although the land in Texas was untamed settlers rushed to buy land for farms."

A. a comma is needed after untamed because the sentence begins with a subordinating conjunction

B. a comma is needed after although because the clauses in the sentence have equal importance

C. this is not a sentence because it does not contain a complete thought

D. a comma is needed when the independent clause begins the sentence