1. ADJECTIVE + TO

2. Disappointed
Glad
Sad
Happy
Anxious
Pleased
Surprised
Proud
Unhappy

3. Able
Unable
Due
Eager
Keen
Likely
Unlikely
Ready
Prepared
Unwilling
Willing

4. We often use the to-infinitive with these
adjectives after it to give opinions:
Difficult/ easy/ possible
Impossible/ hard/ right
Wrong/ kind
Nice/ clever
Silly/ foolish
It’s easy to play the piano, but it’s very difficult
to play well. He spoke so quickly it
was impossible to understand him.

5. http://learnenglish.britishcouncil.org/
en/english-grammar/verbs/infinitive