ambulance用什麼不定冠詞

用不定冠詞an，例如：

1、He didn't even have the intelligence to call for an ambulance.他連呼叫救護車的頭腦都沒有。

2、The injured were rushed to hospital in an ambulance.救護車把傷員火速送往醫院。

3、Someone phone for an ambulance!誰打電話叫輛救護車！