Final answer:
The 5-letter word that pertains to both a group of full-time employees and the set of 5 horizontal lines in music is 'Staff'. It represents both a group of people working together and the structure for noting musical pitches.
Step-by-step explanation:
The answer to the question, which is a 5-letter word that can refer both to a group of full-time employees and the set of 5 horizontal lines on which musical notes are written, is B) Staff.
In the context of an organization, a staff is a group of employees working full-time. It often denotes the personnel that make up an office or company. Alternatively, in the context of music, the staff is a set of five horizontal lines and four spaces that represent different musical pitches. When you are learning how to play the piano, the phrase "Every good boy does fine" is a mnemonic to remember the notes E, G, B, D, and F for the lines of the treble clef, which is a part of the musical staff. Musical notes, like A-sharp, C, or E-flat, are written on the staff, and they are the essential building blocks of a song. Some individuals possess the rare ability to identify these musical notes just by hearing them, which is known as perfect pitch or absolute pitch.