Which of the following is a proper defintion of "maturity intermediation" for financial institutions $($FIs$)?$

A$.$

It means FIs help to reduce information costs between investors and corporations.

B$.$

It means FIs help to transfer wealth from a more mature generation to a younger generation.

C$.$

It means the maturities of FIs' assets and liabilities are mismatched.

D$.$

It means FIs create portfolios of corporate or government bonds with different maturities.