Tissues combine together to form organs which combine together to form organ systems.

Concept: Tissues are formed by clusters of cells. Tissues combine together to form organs which combine together to form organ systems.

Plants have three types of tissues namely, meristematic, permanent, and protective tissues. Permanent tissues can further be divided into simple permanent tissues and complex permanent tissues because of the level of their complexity. Simple permanent tissues are formed by the same kind of cells and hence are considered to be homogeneous. 

Hence, the correct answer is option A.