People who have a primary immunodeficiency disease are most at risk for which of the following?

The correct answer is (B) Infections.

Individuals with primary immunodeficiency diseases have weakened immune systems, which makes it difficult for their bodies to fight off infections. As a result, they are at a higher risk of developing various infections compared to those with a healthy immune system. If you have further questions or need more detailed explanations, feel free to ask!