Answer the following question given this paragraph: 

Microfilaments , shown in Figure below (b) , are made of two thin actin chains that are twisted around one another. Microfilaments are mostly concentrated just beneath the cell membrane, where they support the cell and help the cell keep its shape. Microfilaments form cytoplasmatic extensions, such as pseudopodia and microvilli, which allow certain cells to move. The actin of the microfilaments interacts with the protein myosin to cause contraction in muscle cells. Microfilaments are found in almost every cell, and are numerous in muscle cells and in cells that move by changing shape, such as phagocytes (white blood cells that search the body for bacteria and other invaders).


Q: What structures formed of twisted actin chains are found in almost every cell, and are numerous in muscle cells and cells that move by changing shape?

 Choices:

- RNA

- DNA

- vesicles

- microfilaments

A:
microfilaments
