A - пишется когда слово начинается с согласный букв. an- когда слово всегда начинается гласным. Например: 1) a toy was lying on the floor a dress which costs $50. 2) An Elephant was taking shower with its own trunk... an imergency help was needed to the lost animals which got injured.
2) An Elephant was taking shower with its own trunk... an imergency help was needed to the lost animals which got injured.