Bob has a good friend, Caesar. He is a brown dog. He is not very old. Bob gets him from Mr. Mason. One day Bob's father, mother and Bob go to the Mason's farm   for lunch. After lunch, Mr. Mason says, "I'm going to a big city. So I can't take him there. You can't have a young dog in a big city." " Let me have him, Mr. Mason.  He knows me well and we have no dog, " Mr. Mason looks at Bob's mother and father. "Please , Mother, let me have him," says Bob. "Ask your father," says she. "Please, Dad?" "Yes, you can have him." "Thank you, dear dad. Thanks, Mr. Mason. Come here, Caesar." "See! The dog is his now," says Mr. Mason. How old is the dog? It's  _  .
very old not very old half a year one year and a half