Tommy was walking to his friend’s house when he saw a man walking toward him. The man said hi to Tommy. Tommy stopped and said hello to the man, although he didn’t know him. The man asked Tommy if he would come with him to his car and show him how to use his cell phone. Tommy didn’t think he should do this, because he didn’t know the man. He told the man that he didn’t have time, but the man insisted. When Tommy tried to walk away, the man grabbed his arm and started pulling him toward his car. Tommy yelled as loudly as he could. A policeman came and made the man get away from Tommy. Tommy then ran to his friend’s house and told him what had happened. When his friend’s mother went outside to try and find the man, she saw the policeman arresting him. Tommy was glad he had listened to his mother about strangers.

What is the theme of the above passage?