I knew he had an axe to grind and turned down his offer of help.

Options

A. a blunt axe
B. a sharp tongue
C. a private interest to serve
D. a tendency to fight

Answer

C

Explanation

an axe to grind : to have private reasons for being involved in something or for arguing for a particular cause He claimed to be disinterested, but I knew he had an axe to grind. The best option is a private interest to serve.