The following question, consist of two words each that have a certain relationship to each other, followed by four lettered pairs of words. Select the lettered pair that has the same relationship as the original pair of words: Ink : Pen :: Blood : ?

The answer is Vein.

Ink is used in a pen to write. Blood is used in a vein to transport oxygen and nutrients throughout the body.

A donation is

a gift of money or property to a charity or other organization. An accident is an unexpected and unplanned event that causes damage or injury. A doctor is a person who is qualified to diagnose and treat medical conditions.

Of the four options, only vein is used in the same way as ink is used in a pen.