Question

mosses ( or bryophytes) are considered to be very primitive plants. they differ from advanced plants like large trees because ....
they lack vascular tissue which allows them to grow large and in dry areas.
they do not grow wood and fruit like trees.
they produce with spores only and do not have alternation of generations.
their seeds are very small and must land in water in order to germinate

Explanation:

Mosses (bryophytes) are non-vascular plants, which is the key distinction from vascular advanced plants like trees. Vascular tissue (xylem and phloem) enables large growth and survival in dry areas, which mosses cannot do. Other options are incorrect: mosses have alternation of generations, they don't produce seeds, and lack of wood/fruit is not the primary defining difference.

Answer:

They lack vascular tissue which allows them to grow large and in dry areas.