Final answer:
The Hogwarts ghosts mentioned in the question are The Grey Lady, Nearly Headless Nick, and The Fat Friar.
Step-by-step explanation:
The Hogwarts ghosts mentioned in the question are:
- The Grey Lady - also known as Helena Ravenclaw, she is the ghost of Ravenclaw House.
- Nearly Headless Nick - the ghost of Gryffindor House, whose beheading was almost successful.
- The Fat Friar - the ghost of Hufflepuff House.