When mortgage start defaulting

The catch-up effect refers to the idea that

a. saving will always catch-up with investment spending. b. it is easier for a country to grow fast and so catch-up if it starts out relatively poor. c. population eventually catches-up with increased output. d. if investment spending is low, increased saving will help investment to "catch-up."

What's the most common way for a central bank to increase the money supply?

A. Sell bonds to the public B. Buy bonds from the public C. Collect higher taxes D. Buy bonds from the government