The question asks to find the relationship between 'Knife' and a missing word, based on the relationship between 'Pen' and 'Write'. This is an analogy problem.

Analogy Logic: Tool and Function

The relationship between the first pair, Pen : Write, is that a 'Pen' is a tool used for the action 'Write'.

Applying Logic to Knife

We need to find a word that represents the primary function or action associated with a 'Knife', similar to how 'Write' is associated with 'Pen'.

• A Knife is a tool.
• Its primary function is to Cut.

Evaluating Options

• Option 1: Cut - This matches the primary function of a knife.
• Option 2: Shoot - This is not the primary function of a knife.
• Option 3: Blood - This is a potential result, not the function itself.
• Option 4: Vegetable - This is an object that can be acted upon, not the action.

Therefore, the word that completes the analogy is 'Cut'.