The correct option is A Middle lamella
The primary cell wall, generally a thin, flexible and extensible layer formed while the cell is growing. The secondary cell wall, a thick layer formed inside the primary cell wall after the cell is fully grown. It is not found in all cell types. Some cells, such as the conducting cells in xylem, possess a secondary wall containing lignin, which strengthens and waterproofs the wall. The middle lamella, a layer rich in pectins. This outermost layer forms the interface between adjacent plant cells and glues them together. Therefore, the correct answer is option A.