"I studied in my room."
"Was your roommate there?"
"I think he was."
"Where were you Thursday night?"
"I was home, I think. My roommate was out that evening. When he came in I had retired."
"How about Saturday evening?"
"I went out with a friend and went to the theater."
"Who took supper with you Friday evening?"
"I think I was alone."
"Where did you eat?"