C.

Six

Autotrophs are organisms which are capable of synthesizing their food themselves from organic and inorganic substances.

D.

One

The spore of Equisetum germinate shortly after shedding and give rise to form prothallus. Prothalli of Equisetum are basically monoecious and the gametophytes are rarely seen.
The simplest known sporophyte among bryophytes is that of Riccia while highest evolved known is Bryopsida (Polytrichum, Pogonatum).
Sexual reproduction in Volvox is oogamous type.
The spores in slime molds (e.g., Physarum) are haploid, unicellular usually globose with smooth, spiny or reticulately thickened cell walls.

B.

Salvinia – Prothallus

Salvinia is a heterosporoues water fern. The microsporangia and megasporangia are borne within special reproductive structure called sporocarps. These are borne terminally in clusters on the segment of submerged leaves. Sporocarps are strictly monosporangiate, i.e., they bear either only microsporangia or megasporangia.
Viroids are single stranded RNA molecules. The female reproductive organ is archegonia in gymnosperms.

A.

Protista

RH Whittaker (1969) divided all living organisms into five kingdoms namely Monera, Protista, Fungi, Plantae and Animalia.

A.

Zinc

Carboxypeptidase is synthesized and secreted by the exocrine cells of pancreas. Zn²⁺ is required for the activity of carboxypeptidase, carbonic anhydrase and alcohol dehydrogenase.