Despite the pervasive optimism surrounding the project's launch, several key stakeholders remained _____ about its long-term viability, citing persistent logistical hurdles.

✓ Correct Answer: Option C

The phrase 'despite the pervasive optimism' indicates a contrast, meaning the stakeholders were cautious or wary. 'Circumspect' means careful to consider all circumstances and possible consequences, which fits the context of citing 'persistent logistical hurdles'.