Which of the following is a TRUE statement?

a$.$

High self$-$monitors rarely vary their responses to specific challenges.

b$.$

There are common personality types for a given country.

c$.$

Psychopaths are never successful in the workplace.

d$.$

It is estimated that about $25\%$ of the North American population are psychopaths.

e$.$

High self$-$monitor employees show less commitment to their organizations, but receive better performance ratings.