"Two triangular structures with common base" is the description of the structure of _ of T4 phage.

Explanation

The two triangular structures with a common base that you are referring to are called whiskers. They are located on the collar of T4 phage, which is a ring of proteins that surrounds the base of the tail. The whiskers help T4 phage to attach to the host cell by binding to specific molecules on the cell surface.The whiskers are made up of two identical triangular structures that are connected at their bases. Each triangular structure is made up of about 20 copies of a protein called gp12. The gp12 proteins are arranged in a helix that forms a rigid structure that helps the whiskers to penetrate the host cell.The whiskers are a vital part of the infection process for T4 phage. They allow the phage to attach to the host cell and inject its DNA, which is essential for the phage to replicate and infect new host cells.