Male and female gametophytes are independent and free-living in:
Mustard
Castor
Pinus
Sphagnum
Correct answer: Sphagnum
Solution
Sphagnum is a bryophyte, and in bryophytes the gametophyte is the main plant body and lives independently. In mustard, castor, and Pinus, the gametophytes are highly reduced and dependent on the sporophyte.