Pure substance grade 7

Explanation:

In the more general sense, a pure substance is any homogeneous mixture. That is, it is matter that appears uniform in appearance and composition, no matter how small the sample size. Examples of pure substances include iron, steel, and water. Air is a homogeneous mixture that is often considered to be a pure substance.

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;