Answer:
c) but some of Baldur’s magic food was given to the prince, and it made him as strong as baldur.
Step-by-step explanation:
The original sentence contains a Perfect Continuous Conditional which is usually used in third conditional sentences, Thus, it expresses an unreal and impossible situation that never actually happened. However, the prince had Baldur's food, and as a result of that he became as strong as him.
Option B is wrong because it mixes Present Simple and Past Simple. Finally, option D fails to have noun-verb agreement because food is uncountable and cannot be followed by a plural verb like were.