This is the evolutionary trend of terrestrial plants.
Seedless non-vascular plants have a large gametophyte stage, with a small dependent sporophyte. ------->Seedless vascular plants have a large sporophyte stage, with a smaller independent gametophyte. -------->Seed plants have an even more reduced gametophyte stage, that is completely dependent on the very large sporophyte stage.
a. Dandelion is a seed plant (angiosperm), so its gametophyte is dependent on the sporophyte.
c. Oak is a seed plant (gymnosperm), so its gametophyte is dependent on the sporophyte.
d. A moss is a seedless non-vascular plant (bryophyte), so its sporophyte is dependent on the gametophyte.
Answer is B. Ferns are seedless vascular plants (Pterophyte), and are known for their free-living, photosynthetic, independent gametophytes.