A / An / The

___ books (an / the)

___ starfish (a / an)

___ alligators (an / the)

___ spider (a / an)

___ beaver (a / an)

___ castle (a / an)

___ ball (a / an)

___ octopus (a / an)

___ elf (a / an)

___ moon (an / the)

___ shoes (a / the)

___ scarf (a / an)