goodidea前面加什麼

前面加冠詞a，例如：

1、It would be a good idea to call before we leave.我們出發之前打個電話是個好主意。

2、It seemed like a good idea at the time， and then it all went horribly wrong.那在當時似乎是個好主意，但後來卻鑄成大錯。

3、It seemed like a good idea at the time.當時這主意好像不錯。