Fiduciary relationships are characterized by trust, confidence, and reliance between the parties involved. These relationships are based on a higher standard of care, where one party is obligated to act in the best interest of the other. In this case, the correct answer is option 'D', which means all of the given relationships (parents and child, client and solicitor, doctor and patient) are examples of fiduciary relationships. Let's discuss each of these relationships in detail:

1. Parents and Child:
Parents have a fiduciary duty towards their children. They are responsible for providing care, support, and guidance to their children. Parents are expected to act in the best interest of their children, making decisions that promote their well-being, safety, and development. This fiduciary duty is based on the trust and reliance that children place in their parents.

2. Client and Solicitor:
A solicitor-client relationship is a fiduciary relationship. When a client engages a solicitor for legal advice or representation, the solicitor is obligated to act in the best interest of the client. This includes maintaining confidentiality, avoiding conflicts of interest, and providing competent and diligent legal services. The solicitor must prioritize the client's interests above their own.

3. Doctor and Patient:
The doctor-patient relationship is also a fiduciary relationship. When a patient seeks medical advice or treatment from a doctor, they trust that the doctor will act in their best interest. Doctors have a duty to provide competent and ethical medical care, maintain patient confidentiality, and avoid any conflicts of interest. They must prioritize the well-being and health of their patients.

In all of these relationships, there is a power imbalance, where one party is in a position of trust and authority, and the other party relies on their expertise, guidance, or care. The fiduciary duty arises from this power imbalance and the expectation that the party in the trusted position will act in the best interest of the other party.

In conclusion, all of the given relationships (parents and child, client and solicitor, doctor and patient) involve fiduciary relationships. These relationships are characterized by trust, confidence, and the obligation to act in the best interest of the other party.