The majority of collagen found in human connective tissues is Type I collagen.

- Type I collagen is the most abundant form of collagen in the human body and is a major structural component of skin, bone, tendons, ligaments, and other connective tissues. It provides strength and tensile resistance, making it essential for maintaining the integrity and function of these tissues.

In contrast:
- Type II collagen is predominantly found in cartilage, where it helps provide resistance to pressure.
- Type III collagen is often found alongside Type I collagen in tissues such as skin and blood vessels, but it constitutes a smaller proportion.
- Type IV collagen forms the basement membranes, a specialized form of extracellular matrix that supports epithelial and endothelial cells.

Thus, the correct answer is Type I because of its prevalence and critical structural role in most connective tissues.