Critical reasoning — identify implicit assumptions Statement: In Mumbai (Bombay), railway trains are indispensable for suburban residents to reach their workplaces on time. Assumptions: I. Railway trains are the only transport mode available in the suburbs. II. Only railway trains run punctually.

Introduction / Context:
The claim is that suburban trains are indispensable for commuters to reach work on time. “Indispensable” means necessary or practically unavoidable. We must determine whether this statement commits to exclusivity of mode or to trains being the only punctual option.

Given Data / Assumptions:

• Claim: Trains are indispensable for timely commuting in Mumbai suburbs.
• Assumption I: Trains are the only available mode (exclusivity of availability).
• Assumption II: Only trains are punctual (exclusivity of punctuality).

Concept / Approach:
Indispensable does not mean “only available” or “only punctual.” It means other available modes are, in practice, insufficient to guarantee timeliness (due to congestion, cost, reliability, or capacity). The statement does not require trains to be the sole mode nor the sole punctual service, just that alternatives are not adequate substitutes.

Step-by-Step Solution:

Verification / Alternative check:
Consider practical commuting: multiple modes exist, yet only trains can handle huge peak-hour loads efficiently. This supports indispensability without exclusivity claims.

Why Other Options Are Wrong:

• Only I / Only II / Either / Both: Each injects an unnecessary exclusivity condition not entailed by “indispensable.”

Common Pitfalls:
Equating “indispensable” with “only”; overlooking factors like capacity and speed that make one mode necessary even when others exist.

Final Answer:
Neither I nor II is implicit