C. Sometimes the ‘to-infinitive’ gives a reason for the adjective: disappointed, glad, sad, happy, anxious, pleased, surprised, proud, unhappy, and other adjectives with the ‘to-infinitive’ are: able, unable, due, eager, keen, likely, unlikely, ready, prepared, unwilling, willing
C1. 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
D. We use the preposition ‘for’ to show who these adjectives refer to: difficult, easy, possible, impossible, hard
D1. use the preposition ‘of’ with other adjectives.
E. As a postmodifier after abstract nouns like: ability, desire, need, wish, attempt, failure, opportunity, chance, intention
E1. We often use a to-infinitive as a postmodifier after an indefinite pronoun.
F. We also use ‘to ~’ after seem, appear, tend, pretend, claim
F1. There is also a continuous infinitive (to be doing) and a perfect infinitive (to have done)