Final answer:
Land plants have multicellular gametangia and exhibit alternation of generations, whereas Charales lack this feature even though they share other characteristics with land plants.
Therefore the correct answer is option is b) Multicellular gametangia
Step-by-step explanation:
The characteristic that is present in land plants and not in Charales (a type of charophytes) is multicellular gametangia. Charales, while sharing many characteristics with land plants, such as having cell walls with cellulose, chlorophyll a and b, and a form of growth, do not exhibit the land plant characteristic of alternation of generations.
This means they do not have distinct multicellular forms for their haploid and diploid stages, with a gametophyte and sporophyte phase, respectively. The mentioned characteristic allows for the formation of specialized structures for reproduction, which is a key feature that has enabled land plants to colonize a variety of terrestrial habitats.