The correct answer is option 1: blood is a connective tissue. Connective tissues are a group of tissues in the body that play a role in connecting, supporting, and protecting different organs and structures. They are characterized by having cells scattered within an extracellular matrix.

Blood fits this definition because it consists of cells suspended within a fluid matrix called plasma. The cells in blood include red blood cells, white blood cells, and platelets. These cells perform various functions such as carrying oxygen, fighting infections, and assisting in blood clotting. The plasma, on the other hand, contains water, proteins, hormones, nutrients, and waste products.

While blood does have some characteristics that are similar to epithelial tissue, such as its ability to form a barrier, it does not fully meet the criteria for epithelial tissue. Epithelial tissue primarily covers and lines body surfaces, while connective tissue typically supports and connects different tissues and organs.

Therefore, blood is correctly classified as a connective tissue.