Good morning is the correct one.
Good morning is used to say hello politely when people first see each other in the morning; sometimes also used formally when people leave each other in the morning.
In an informal way, you can just say Morning.

Good morning is the correct one.
Good morning is used to say hello politely when people first see each other in the morning; sometimes also used formally when people leave each other in the morning.
In an informal way, you can just say Morning.
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