How would you implement a 1-to-4 demultiplexer using two cascaded 1-to-2 demultiplexers?

How would you implement a 1-to-4 demultiplexer using two cascaded 1-to-2 demultiplexers?

• A. First stage uses S1 to split the input into two lines; second stage uses S0 to route to four outputs.
• B. Use two 1-to-2 demultiplexers in parallel, both driven by the same input.
• C. Use two 1-to-2 demultiplexers in series with independent select signals to produce four outputs.
• D. First stage uses S0 to split the input into two lines; second stage uses S1 to route the selected line to one of four outputs.

Answer: (D)