The basic reason why the commercial banking system can increase its checkable deposits by a multiple of its excess reserves is that:

Multiple Choice

the MPC of borrowers is greater than zero but less than $1.$

the banking system must keep reserves equal to $100$ percent of its checkable$-$deposit liabilities.

reserves lost by any particular bank will be gained by some other bank.

the central banks follow policies that prevent reserves from falling below the level required by law.