Use the correct article (a or an):
... academy, ... album, ... bright album, ... actor, ... great actress, ... arch, ... marble arch,
... chance, ... unlucky chance, ... dove, ... ear, ... elf, ... tiny elf, ... horse, ... hour, ... long
hour, ... institute, ... lemon, ... mill, ... obelisk, ... opera, ... Italian opera, ... owl, ... paper, ...
rabbit, ... quarter, ... train, ... wing, ... voyage, ... year.

Смотри, перед гласной идет an, а перед согласной a