Which of the following is true about first-degree murder?

First-degree murder is defined under California law as a willful, deliberate, and premeditated killing, which involves the element of malice aforethought. This means that the perpetrator acted with the intent to kill and engaged in planning the act before carrying it out.

The concept of malice aforethought is crucial, as it distinguishes first-degree murder from other types of homicide. This classification allows for a range of circumstances wherein the killing may be considered first-degree murder, as long as there is a deliberate intent to take another's life involved. Factors such as the method of killing or the circumstances surrounding the act, such as planning or deliberation, contribute to its classification as first-degree.

The other options present misconceptions about the nature of first-degree murder. It can involve various methods of committing the act, not exclusively with a firearm, and does encompass instances where it occurs during the commission of another crime, given it meets the requisite intent and malice. Overall, understanding the inclusion of malice aforethought in the definition is key to grasping the seriousness and legal implications of first-degree murder in California.