Read the following article and select the best answer. Article: At London College, the boys can go to the city in the afternoon. But they must return to the school before six. And Bob doesn't often obey the rule. One afternoon, Bob walked to the city and went to the cinema. When he got to the school, it was eight o'clock. He was a little worried. He ran quickly to the gate. It was closed. He went round the school building to another door. That one was closed, too. Then he saw an open window on the ground floor. It was the head teacher's office. Bob looked into the room, and no one was there. He quickly climbed up and jumped into the room. Just then he heard a voice. He looked around and hid under the sofa. One minute later, Mr. Scott, the head teacher, came in. He turned on the light and sat down on the sofa. Then he began to read. Bob lay under the sofa and looked at the head teacher's feet for an hour. He could not move. At last the head teacher stood up and walked towards the door. "Thank goodness, he didn't find me under the sofa." thought Bob. Then the head teacher stopped. He turned his head and spoke to the sofa, "Would you mind turning off the light when you leave?" he said and left the office. Question: Mr.Scott knew that _ . - Bob went to the cinema - Bob was in the classroom - Bob returned to the school - Bob was under the sofa
A:
Bob was under the sofa