"I dunno." is a common English expression. It means "I don't know." We say "I dunno"
in conversation when we're speaking quickly. We might also say "I don't know" or "uhduhnuh"
You might hear native English speakers say it this way. So let's practice listening to
this expression. Emma, what is the meaning of life? I don't know. Emma, how long is the memory
of a goldfish? I don't know. Emma, do aliens exist? I don't know. Emma, who invented the
telephone? I know that one. It is Alexander Graham Bell. So try to use "I don't know"
in your everyday conversation. It's a great conversational expression.