Which of the following statements would likely be admissible in court?

A dying declaration is a statement made by a person who believes they are about to die, relating to the cause or circumstances of their impending death. This statement is admissible in court under the exception to the hearsay rule, as it is considered to carry a high level of credibility due to the speaker's belief in their imminent death. The rationale behind this is that individuals on the brink of death are thought to speak with an earnestness and truthfulness that one would not expect in ordinary circumstances.

In contrast, the other options lack the reliability or legal standing needed to be admissible in court. For example, a police officer's opinion may be seen as subjective without factual backing, a witness's speculation is generally not considered helpful to a case as it does not rely on direct knowledge, and unverified hearsay lacks the necessary confirmation of authenticity and trustworthiness to be presented in court. Thus, dying declarations provide a unique exception that allows such statements to be presented, given their context and the gravity of the situation they arise from.