Final answer:
Alexis said she was good under pressure because she remained calm and sensible during tense situations, as indicated by her demeanor and her ability to reassure others.
Step-by-step explanation:
Alexis indicated that she was good under pressure likely due to her capacity to remain calm and sensible even when faced with challenging circumstances. This can be inferred from the context provided where she is described as rising, feeling the relief of a burden lifted, implying she was handling a stressful situation well. Moreover, the tension in the room, hinted by the use of 'mild stiffness' and 'nervousness', and her effort to reassure Lassiter, further supports her ability to stay poised under pressure. Additionally, the extract involving Bernice suggests that confidence plays a role in handling pressure well, as having the foundation of self-confidence from positive social interactions enabled Bernice to manage unfamiliar situations.