Select the most appropriate option that can substitute the underlined segment in the given sentence. Once the CEO joins the office, you can be sure that he will replace most of the staff members. After all, whenever someone new takes control of an organisation he makes many changes.

1. a new broom sweeps clean
2. the grass is always greener on the other side
3. two heads are better than one
4. where there's a will, there's a way