Final answer:
Amir thinks he and Soraya cannot have children due to potential fertility issues with either Soraya or Amir. Soraya's irregular menstrual cycles and Amir's past injuries to his testicles could be contributing factors.
Step-by-step explanation:
Amir thinks he and Soraya cannot have children due to the fact that Soraya has been unable to get pregnant after a year of trying. This may indicate that there is an issue with either Soraya's fertility or Amir's fertility. Soraya's irregular menstrual cycles and longer cycle length could suggest potential issues with ovulation, while Amir's past injuries to his testicles raise concerns about sperm health.