The correct answer is "Ohayou (gozaimasu)". "Ohayou (gozaimasu)" is a common Japanese greeting used in the morning. It is equivalent to saying "Good morning" in English. The other options, "Konnichiwa" means "Hello" or "Good afternoon", "Oyasuminasai" means "Good night", "Ja, mata" means "See you later", and "Odaijini" means "Take care". Therefore, "Ohayou (gozaimasu)" is the appropriate response to "Good morning".