Passage Summary: To get a correct measurement of a boat's hull, you have to use a specific tool called a line level to make it level; however, the scientists who found an old boat didn't know what they were doing and weren't sure if they did this step.

Reasoning: Accurate hull measurement requires leveling the hull with a 'line level,' but the scientists who found a ninth-century boat were inexperienced and unsure if they had leveled it.

Analysis: In a Must Be True scenario, we must treat the premises as absolute laws and see what logically follows without adding any outside info. We know a line level is a requirement for leveling, and leveling is a requirement for accuracy. If the scientists were unsure if they leveled the hull, then they cannot be certain their measurements are accurate. Look for an answer that stays within this chain of requirements—specifically, if the 'line level' wasn't used, the measurement cannot be considered accurate.