We should always be grateful to one who has suffered for a great cause.

The correct answer is: B. Martyr

A martyr is a person who is killed because of their beliefs. They are often seen as heroes, because they are willing to die for what they believe in.

A fanatic is a person who is extremely enthusiastic about something, often to the point of being unreasonable or intolerant of other views.

A devotee is a person who is devoted to a particular person, cause, or activity.

A patriot is a person who loves their country and is willing to defend it.

In the context of the question, the person who has suffered for a great cause is a martyr. They are someone who has died because of their beliefs, and they are often seen as heroes.