A static circuit is one of the types of logic integrated circuits. There are two types of logic, dynamic and static. The most important difference between the two is the clock signal. Static does not use a clock signal; however dynamic does, it uses the clock signal to evaluate combinational logic.
Theoretically you use five 4-to-1 multiplexers. You use four of them to connect the 16 inputs. You then have four outputs. Take the fifth multiplexer and connect the four outputs as the inputs. The fifth multiplexer then has a single output that has multiplexed the original 16 inputs.
Multiplexer is an electronic term. A multiplexer combines input from several sources into one. Individuals familiar with electronic devices, how they work and how to configure them will know which multiplexer to use for which device and under what circumstances.
The concept of multiplexing is that we have 2n inputs but only one of them becomes the output for a given condition (or time). That particular input is selected by the combination of n selection lines.