What is the Securities and Exchange Commission?

1. What is credit rationing? Why would a lender ration credit rather than raise the interest rate it charges on loans?
2. What is the Securities and Exchange Commission (SEC)? Why was it founded? What effect has the SEC had on the level of asymmetric information in the U.S. financial system?
3. What is collateral? How do banks use collateral to reduce adverse selection in making car loans?