Which of the following is correctly matched?

Parthenium hysterophorus (carrot grass) is an alien species introduced inadvertantly for some economic use, turned invasive causing decline or extinction of the indigenous species.
(a) Aerenchyma is found in aquatic plants (Vallisneria, Hydrilla), but Opuntia is a xerophytic plant.
(b) Biome is total sum of all ecosystem present in the planet earth whereas age pyramid is the graphical representation of age of organismas of one population at a specific time.
(d) Stratification is related with different layers of vegetation in an ecosystem (like forest/grass land) and population is a term referred to a group of same kind of organisms which can freely interbreed.