In Figure E6-3, which is the schematic symbol for a NAND gate?

Explanation
Symbol 2 has the flat input side and semicircular output end of an AND gate with an inversion bubble on its output, which is exactly a NAND. Symbol 1 is the same body without the bubble and is a plain AND, symbol 3 is the curved-back OR body, and symbol 4 is that OR body with a bubble, making it a NOR.