Join the following sentences to make one complete sentence without using and, but or so.
He remained absent on Friday. It was foolish of him.
Topic: Synthesis — infinitive
Answer
It was foolish of him to remain absent on Friday.
The neatest combination uses an INFINITIVE, and it requires reversing the order of the two sentences: the judgement comes first and the action becomes the infinitive that follows.
Original: He remained absent. It was foolish of him. Combined: It was foolish OF HIM TO REMAIN absent on Friday.
Note the preposition: "foolish OF him", not "foolish FOR him". With adjectives describing a person’s character or behaviour — kind, foolish, generous, careless — English uses OF. With adjectives describing difficulty or importance — easy, hard, necessary — it uses FOR: "It was easy FOR him to answer."
That distinction is worth learning; it is a frequent source of error.