The major difference in ethnicity, religion, and settlement patterns of California:

A. was founded by Spain, was Catholic, and settled very early in the 18th century
B. they were completely successful in Christianizing the indians
C. the area was dominated by Protestant settlers from northern Europe
D. was attractive to Angelos before 1820 and the MIssouri compromise
E. the Indian cultures dominated the region even after settlement

This was my question before and your helpful link led me to think the answer is A. Is that correct? Thank you so much in advance!

Yes. The answer is A.