哦，我知道了。
Oh, I see.
哦
oh (interjection indicating that one has just learned sth)
interjection HSK 3.0 · Band 5
Watch it being written
Every character draws itself, stroke by stroke. Then grab the brush: trace it yourself and hear the word when you finish.
哦
Nice writing!
See it in sentences
哦，原来是这样。
Oh, so that is how it is.