This question is about finding the word that doesn't fit with the others in a group based on their meanings.
Dishonest, irresponsible, sympathetic, unkind :
'Sympathetic' is different. While 'dishonest,' 'irresponsible,' and 'unkind' have negative connotations, 'sympathetic' has a positive one.
Borrow, charge, invest, salary :
'Salary' is different. While 'borrow,' 'charge,' and 'invest' are actions related to money, 'salary' is an income or payment, not an action.
Boarding, primary, state, head :
'Head' is different. 'Boarding,' 'primary,' and 'state' are types of schools, whereas 'head' refers to the person leading the school.
Arena, coach, sports hall, stadium :
'Coach' is different. 'Arena,' 'sports hall,' and 'stadium' are places, while 'coach' refers to a person involved in sports.
Cast, extra, plot, star :
'Plot' is different. 'Cast,' 'extra,' and 'star' refer to people involved in an acting production, while 'plot' refers to the storyline.
Lips, shoulder, teeth, tongue :
'Shoulder' is different. 'Lips,' 'teeth,' and 'tongue' are parts of the mouth, while 'shoulder' is part of the arm.