This is a common conversation in Spanish, to answer the exercise you need to know classic vocabulary about presentation or starting a conversation. The correct answer of the exercise is ''¿Cómo está?'' because you already know that the answer of the professor is ''estoy bien'', which means there was a question before asking how he was.
1. Yo espero que tú hables español. 2. Espero regresar temprano. 3. Pienso queesun buen hombre. 4. No creo quevengatemprano. 5. Es nesesario quevuelvaspronto.