The antherozoids of fern are

(a) Uniflagellate

(b) Biflagellate

(c) Quadriflagellate

(d) Multiflagellate

In ferns, the antherozoids (male gametes) are multiflagellate and haploid in nature. They are produced in the antheridium, a male reproductive structure that develops during the gametophytic phase of cryptogams such as bryophytes and ferns.

In higher plants, the male gametophyte is reduced to pollen grains, where the antheridium is represented by a single generative cell. During pollination, this generative cell divides to form sperm cells.

The female counterpart of the antheridium in cryptogams is the archegonium, which corresponds to the gynoecium in flowering plants. The antheridium typically consists of sterile cells and spermatogenous tissue. The sterile cells form a protective jacket layer around the spermatogenous tissue, which produces spermatids through mitotic division.

In bryophytes, the antheridium develops on a specialized stalk-like structure called the antheridiophore, which bears the antheridium at its apex.

So, the correct answer is option (D) Multiflagellate.