The band suspects Taki played favorites in choosing Reina in the auditions. Noticing the band's rising distrust of Taki and Reina, he makes a proposal.
Sensei couldn't refuse, then.
لن يقدر المعلّم على رفض الأمر إذاً
Dann konnte Sensei ja schlecht ablehnen.
Supongo que no podía negarse.
Supongo que no podía decir que no.
Le prof n’avait pas 
le choix, en fait.
Allora il professore 
non avrebbe potuto rifiutare.
O professor não se negaria, então.