A: I ran into Ann downtown last week.
B: Really? I have not seen her for a year.
A: She said she went to Japan last year.
B: No wonder.
e.g. I used to run into him from time to time.
e.g. He has run into a girl whose eyes are green color.
No wonder ( that ) = It is no wonder that…
e.g. No wonder you were late--you ate your breakfast so slowly.
e.g. It is no wonder (that) he'll sign the contract tomorrow.