A guard noticed the leak. Select the standard relative-clause version with no resumptive subject.
The guard which he noticed the leak raised the alarm.
The guard who he noticed the leak raised the alarm.
The guard that he noticed the leak raised the alarm.
The guard who noticed the leak raised the alarm.✓Respuesta correcta
Explicación
Who is the subject of noticed and directly links that action to the guard. Who he is the closest distractor because he unnecessarily repeats the guard as a second subject inside the clause.