Final answer:
The correct answer is 'pump,' a high-heeled, slip-on shoe with a V-shaped throat, commonly worn for formal occasions.
Step-by-step explanation:
The 4-letter word that describes a high-heeled, slip-on shoe with a low-cut or V-shaped throat is 'pump'. It is neither a boot, which typically covers the ankle and sometimes the lower leg; nor a sandal, which is open and strappy; and certainly not a sock, which is a piece of clothing worn on the feet. Pumps are classic shoes that are often worn on formal occasions or in professional settings, and they are known for being both stylish and somewhat formal.