Statement: The largest domestic airline announced a new summer schedule, introducing more flights on trunk routes.\nAssumptions:\nI. More passengers are expected to travel by this airline on trunk routes during summer.\nII. Other airlines will also increase flights across all sectors.

Introduction / Context:
Capacity expansion on trunk routes for summer signals demand expectations. We must separate what this airline presupposes from industry-wide projections.

Given Data / Assumptions:

• Action: add flights (supply increase) on trunk routes in summer.
• Purpose: meet anticipated demand and improve connectivity.

Concept / Approach:
The decision rests on Assumption I: expected higher passenger traffic for this airline on those routes in summer. Assumption II is speculative about competitors and not required for this firm’s scheduling choice.

Step-by-Step Solution:
1) Without I, adding flights would be unjustified.2) II concerns rival responses and is irrelevant to the internal rationale.

Verification / Alternative check:
Timetables are set on own-demand forecasts; competitor actions are considered but not assumed.

Why Other Options Are Wrong:
They either ignore the clear demand premise or import unnecessary market-wide predictions.

Final Answer:
Only Assumption I is implicit.