pupils oFtEn wAnt to sit nExt to thEir pArtiCulAr FriEnD AnD mAny ClAssroom ACtivitiEs involvE moving ABout, But EvEn rElAtivEly smAll AltErAtions CAn mAkE ______ to thE visuAl ComFort oF pupils with sight DEFECts.
A．A DiFFErEnCE
B．An intErFErEnCE
C．A moDiFiCAtion
D．An impACt