What part of speech is the word "well"?

The team doctor decided that Mona was well enough to play in Saturday’s championship game.]]> What is "well" modifying?

The team doctor decided that Mona was well enough to play in Saturday’s championship game.]]> The team doctor decided that Mona was well enough to play in Saturday's championship game. Type the correct form of the underlined modifier into the box, then submit it and say the sentence.

The team doctor decided that Mona was well enough to play in Saturday’s championship game.]]>