Today is the fifth day of August. It is Judy's birthday. When she comes back home from school, she sees a card on the table. It says, "There's a present (礼物) for you, Judy. Look for it in your bedroom." Judy runs into her bedroom. Her parents are looking at her andsmiling. On the chair she sees a red box. She thinks her present must be in it. She opens it, and there is a piece of paper in it. She reads it, "Dear Judy, I'm your present. My first letter is in the word 'bag', but not in 'age'. My second letter is in 'like', but not in 'lake'. My third letter is in "know", but not in 'now'. And you can find my last letter in both 'desk' and 'get'. What am I?" Judy thinks for a while and says, "Aha, I know. But where is it?" Her father tells her it is in her study.
What is it? Do you know?