“罗马法对债权的规定和解释是一项重要内容。它制定了解决各类债务纠纷时适应的条款，而且特别明晰地规定了契约的各种形式，以及契约双方的权利和义务。”材料反映出罗马法的核心内容是

A．法律面前人人平等

B．保护私有财产

C．调整公民与非公民的关系

D．重视以证据定罪

During the class, Tom slipped out of the classroom ____the back door so as not to be found by the teacher.

A．across

B．in

C．by

D．beside