The correct option is C The lion had killed his friend, the donkey
"With a great roar, he leapt upon the donkey. The rooster, watching from the farmyard, said, “Alas! My poor friend did not realize what he could not do.”" - this line from the passage supports the assumption that the rooster was sad because the lion had killed his friend, the donkey. From the given choices, B is the best answer.