Could be false. We only know that the scientists weren’t sure they had leveled the hull; we don’t know definitively that they did not do so. Also, we do not have enough information to guarantee the causal claim that (A) makes.

Could be false. (B) can be represented as “level the hull→ measure accurately,” which reverses the sufficient and necessary conditions given in the sitmulus.

Could be false. (C) makes a causal claim that we cannot justify from the information in the stimulus.

Must be true. We know that using a line tool is a necessary condition of measuring accurately.

Could be false. Experience with measuring hulls isn’t a necessary condition of measuring accurately.