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You are both incorrect and correct.
The diagram you attached has 4 Full Adders, but the lsb only need a Half Adder if the Carry-in is hard tied LO (or not even present), so an N-bit adder requires 1 Half Adder and (N-1) Full Adders.
But it is depressing that, after all of this discussion, you still had to go find a diagram of a 4-bit adder instead of being able to draw one from scratch. That doesn't bode well for you ability to develop the skills necessary to design circuit since, pretty much by definition, designing something involves creating something you can't just Google and find an example done by someone else (pieces of the design, maybe, but if the whole thing already existed on the net, they wouldn't be paying you to design it).
The diagram you attached has 4 Full Adders, but the lsb only need a Half Adder if the Carry-in is hard tied LO (or not even present), so an N-bit adder requires 1 Half Adder and (N-1) Full Adders.
But it is depressing that, after all of this discussion, you still had to go find a diagram of a 4-bit adder instead of being able to draw one from scratch. That doesn't bode well for you ability to develop the skills necessary to design circuit since, pretty much by definition, designing something involves creating something you can't just Google and find an example done by someone else (pieces of the design, maybe, but if the whole thing already existed on the net, they wouldn't be paying you to design it).
