The correct answer is option 4, skeletal muscle.

Connective tissue is a type of tissue that connects, supports, and protects other tissues and organs in the body. It is characterized by an abundance of extracellular matrix and cells that produce and maintain the matrix.

Option 1, bone, is a type of connective tissue. It is composed of cells called osteocytes embedded in a matrix of calcium salts and collagen fibers. Bone provides structure, support, and protection to the body.

Option 2, cartilage, is also a type of connective tissue. It is made up of cells called chondrocytes within a matrix of collagen fibers and proteoglycans. Cartilage provides cushioning and support to joints, as well as structure to various body parts like the nose and ears.

Option 3, blood, is considered a connective tissue as well. It consists of cells (red blood cells, white blood cells, and platelets) suspended within a liquid matrix called plasma. Blood transports oxygen, nutrients, hormones, and waste products to and from cells.

However, option 4, skeletal muscle, is not a connective tissue. Skeletal muscle is a type of muscle tissue responsible for voluntary movements. It is made up of