The Securities Investor Protection Corporation (SIPC) protects customer accounts against the failure of a member brokerage firm. The total protection for each separate customer is up to $500,000. However, within this total limit, there is a specific sub-limit for cash balances, which is capped at $250,000. In this scenario, the investor has $300,000 in cash. Despite the cash balance being higher, SIPC coverage for the cash portion is limited to the maximum of $250,000. The remaining $250,000 of the total $500,000 coverage would apply to the securities.

A. $150,000 is not a recognized SIPC coverage limit for cash or securities.

C. $300,000 is the investor's cash balance, but it exceeds the maximum SIPC cash protection limit of $250,000.

D. $700,000 is the total account value, which exceeds the overall SIPC protection limit of $500,000 per customer.

1. Financial Industry Regulatory Authority (FINRA). "Securities Investor Protection Corporation (SIPC)." FINRA.org. Accessed 2023. This official documentation states, "The limit of SIPC protection is $500,000, which includes a $250,000 limit for cash."

2. Securities Investor Protection Corporation (SIPC). "What SIPC Protects." SIPC.org. Accessed 2023. The primary source document specifies, "SIPC protects against the loss of cash and securities...The limit of SIPC protection is $500,000, which includes a $250,000 limit for cash."

3. University of Illinois, College of Agricultural, Consumer and Environmental Sciences. Pring, G.A. "Securities Investor Protection Corporation (SIPC)." Investor Education, Publication Number: F-P-SIPC. This university courseware states, "SIPC provides coverage up to $500,000 per customer... This coverage includes a maximum of $250,000 for cash claims."