Which of the following statements best describes the characteristic of bacilli?

Bacilli are indeed best described as rod-shaped bacteria. This characteristic is fundamental to their classification within the broader category of bacteria. Bacilli are one of several shapes that bacteria can adopt, including cocci (spherical) and spirilla (spiral-shaped). Their rod-like structure is significant in various biological processes and affects how they interact with their environment, including their role in diseases or beneficial functions in certain ecosystems.

While some bacilli can indeed be harmful to humans, stating that they are primarily harmful without context is misleading, as many bacilli are not pathogenic and can even be beneficial. The process of reproduction by binary fission is common among many bacteria, regardless of shape, and does not specifically define bacilli uniquely. Therefore, the most accurate characterization of bacilli focuses solely on their rod shape.