What must you do to obtain a California driver license?

Answer: D — Submit a written test.

Obtaining a California driver's license requires passing a written test. This verifies that the individual understands the rules and regulations of driving in California. Options A, B, and C may also be required, but they do not address the specific requirement of passing a written test to obtain a license. Option A may be required to prove that the individual is eligible to apply for a license in the first place, while options B and C may be needed in different situations, such as purchasing car insurance or traveling outside of the country. However, none of these options specifically address the task of obtaining a California driver's license. Therefore, the correct answer is D.