This is a very common question from beginner learners.
First of all, let’s see Hiragana, Katakana and Kanji look like.
For example, I will say,
My name is Terumi Kai.
Hiragana version
わたしのなまえは、かいてるみです。
Katakana version
ワタシノナマエハ、カイテルミデス。
Kanji version
私の名前は、甲斐輝美です。
The correct sentence is the Third one.
The first version is the level of 6, 7 years old kids in Japan that they don’t know Kanji so they write only in Hiragana.
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