Aaron: are we writing an essay tomorrow?
Eric: yep...
Erasmus: what? I have an appointment and I wont be able to go
Aaron: don't forget to take the dcument from the doctor which will explain your absence
Erasmus: thank you for reminding me of that, otherwise this rat would not let me write it again 
Erasmus can't write an essay tomorrow. He should take an excuse from the doctor for his absence. 