Healing by secondary intention occurs when:

Healing by secondary intention involves scenarios where a wound is left open and heals naturally, as opposed to being closed directly with sutures or staples. This type of healing typically occurs in larger wounds or those in which there is significant tissue loss.

When a wound heals by secondary intention, the body initiates various processes, including inflammation, granulation tissue formation, and epithelialization. In particular, the process of wound contraction plays a significant role; this is where the surrounding skin and tissue pull inward to help close the wound. Myofibroblasts, which are specialized cells in granulation tissue, contribute to this contraction, leading to a reduction in the overall size of the wound.

The other options do not accurately describe secondary intention. For instance, healing with primary suturing involves directly closing the wound edges and is classified as primary intention, where there is minimal scarring. Additionally, while fibroblast proliferation is a key aspect of wound healing, merely decreasing in size due to this proliferation alone does not encompass the entire process of secondary intention, nor does healing without scarring accurately describe the outcome typically associated with this type of healing. Option C captures the essence of how wounds heal by secondary intention through the mechanism of contraction.