Antonio aprobó todas las asignaturas. No lo puede creer porque no había estudiado nada.Antonio passed all his subjects. He can't believe it because he hadn't studied at all.
Ana no se fía de ese político. Cuando promete algo, no lo puede creer.Ana doesn't trust that politician. Whenever he promises something, she can't belive him.
Cuando Luis dice que va a dejar de fumar, su esposa no lo puede creer. Lo ha dicho tantas veces.When Luis says that he's going to quit smoking, his wife can't believe him. He's said it so many times.
2.
Una palabra o frase que se usa para hablar de la segunda persona formal usted (p. ej. ¿Dónde está usted?).
No entiendo por qué dice que no lo puede creer. A mí me parece perfectamente posible.I don't understand why you're saying you can't believe it. It seems perfectly possible to me.