My guess (and I didn’t read the rest of the comments): There will be an output of 1 only if A,B,C is 1. If any of A,B or C is 0, the AND gates at the left won’t activate no matter what D does.

Example: 1 is 001, 2 is 010, 3 is 011, 4 is 0100, 5 is 0101,… 15 is 1111, and so on. ... The LED would be ON if the current flows through the circuit. For the current to flow, one of the switches must ...

Logic synthesis tools also allows for technology independent designs. Logic synthesis technology was commercialized around 2004, and since then it’s been part of the standard EDA tool chain for ASICs ...