Final answer:
The metal bar can be measured to the nearest tenth of a centimeter by Ruler B and to the nearest hundredth of a centimeter by Ruler A, making option C the correct choice.
Step-by-step explanation:
The greatest degree of precision to which the metal bar can be measured by Ruler A and by Ruler B is related to the smallest increments each ruler can measure. Ruler A can measure to the nearest hundredth because it has markings for tenths of a centimeter and allows the user to estimate to the hundredths. On the other hand, Ruler B, with centimeter and millimeter markings, provides measurements to the nearest tenth of a centimeter (millimeter).
Therefore, Ruler A gives a measurement that can be rounded to 2.55 cm, indicating two certain digits (2 and 5) and one estimated (hundredths place), whereas Ruler B's measurement of 2.5 cm has only one certain digit, the whole number (2), and one estimated (the tenths place).
Basing on the precision of measuring tools and significant figures, the correct answer is option C: to the nearest tenth by Ruler A and to the nearest hundredth by Ruler B.