Which of the following are examples of invasive meningococcal diseases?

The correct choice is based on the nature of invasive meningococcal diseases, which are primarily caused by the bacterium Neisseria meningitidis. This pathogen can lead to two significant and severe conditions: meningitis and septicemia.

Meningitis refers to the inflammation of the protective membranes covering the brain and spinal cord, which can lead to critical complications such as neurological damage or death if not treated promptly. Septicemia, or bloodstream infection, occurs when the bacteria enter the bloodstream, leading to systemic symptoms and potentially severe outcomes like septic shock.

In contrast, the other options list conditions that are not classified as invasive meningococcal diseases. Urethritis, pneumonia, conjunctivitis, otitis, sinusitis, and similar conditions are typically localized infections that do not involve the systemic spread associated with invasive diseases caused by Neisseria meningitidis. Therefore, these conditions are not indicative of the severe manifestations that define invasive meningococcal disease, making B the accurate representation of such cases.