Final answer:
Dave cannot insure Angela's partner without establishing an insurable interest and obtaining their consent, as typically required when initiating a life insurance policy for an adult.
Step-by-step explanation:
In the scenario presented, Dave is involved in multiple relationships that could influence his ability to purchase life insurance policies. Dave has a vested interest in insuring members of his family and business partner. However, when considering who Dave cannot insure in this scenario, we must consider insurable interest and the concept of consent.
The one person Dave cannot insure is likely Angela's partner, as the example provided does not suggest any financial dependency or business relationship between Dave and this partner, which is required to establish an insurable interest. Life insurance policies generally require an insurable interest at the time of policy initiation. Insurable interest means that the policyholder would suffer a financial loss or certain other types of losses if the insured person were to pass away. Furthermore, purchasing a life insurance policy on an adult typically requires their consent, which may not be obtainable in the case of Angela's partner.