Delbert had his laptop computer stolen from his office during a recent holiday weekend. He went to Alice's computer resale shop to find a replacement and saw what he mistakenly thought was his computer. He questioned Alice, who told him that someone had just sold her the computer a few days ago, but she refused to give him any information on the seller and would not let him inspect it more closely. That night, after the shop was closed, Delbert forced open the back door and took the computer. Alice's clerk, who lived in an apartment above the shop, heard someone breaking in and called the police. Delbert was apprehended a block away from the building. If Delbert is charged with burglary in a jurisdiction retaining the common law criminal offenses, which of the following facts will be most relevant in determining his guilt or innocence?
A. His mistake as to the identity of the computer was not reasonable.
B. He was unaware that there was an apartment above the shop and did not believe that anyone lived in the building.
C. He realized that the computer was not his before he carried it out.
D. None of the above facts are relevant. 
Choose A, B, C or D as your solution.
B