What are the two essential elements of a criminal offence?

The two essential elements of a criminal offence are indeed the act and the intention. This is often referred to in legal terms as "actus reus" and "mens rea."

"Actus reus" refers to the physical act or conduct that constitutes a crime; it is the action or behavior that breaches the law. For example, stealing an item is the act itself that can lead to criminal liability.

"Mens rea," on the other hand, refers to the mental state or intention of the individual at the time the act was committed. It pertains to whether the person intended to commit the crime, which is crucial for establishing guilt. For instance, if someone accidentally breaks a law without the intent to harm or commit a crime, this lack of intention may result in a different legal consequence compared to someone who purposefully commits the act.

The other choices illustrate different aspects of criminal law but do not encapsulate the core components necessary for establishing a criminal offence. For example, motive and opportunity relate to why a person might commit a crime and their capacity to do so, but they do not constitute the legal requirements for proving a criminal offence. Legal justification and consequences are relevant but are not the foundational elements needed to categorize an act as a crime.