Final answer:
The phrase describes a person who remains steady in stressful situations, corresponding to option 4; a person who is unaffected by stress.
Step-by-step explanation:
The phrase 'Very calm and composed and untroubled by stress' refers to an individual who maintains a state of calmness and self-control without being disturbed by stress or difficult situations. This means that the person does not let stress affect them in a negative way and remains steady and poised even in challenging circumstances.
Option 4 (unaffected by stress) is the correct answer as it clearly aligns with the description given by the phrase. This person differs from those who may experience higher levels of stress, which according to the Eysencks' theory, would score lower on neuroticism, thereby exhibiting more stability in stressful situations.