How does Gregor feel about his fathers transformation?

Surprised that his father became healthy.

surprised and somehow saddened.

Explanation:

In Kafka's novella, Metamorphosis, Gregor finds himself one day turned into some sort of bug, which brings disgust to his family, mostly to his father. Since Gregor can't go to work anymore, the father needs to return to work to provide for his family. This brings certain beneficial health improvements for the father, but, as he grows healthier, he also starts loathing his son's condition, and his son in general, more and more.