Enzymes in nucleic acid metabolism:

• DNA ligase catalyzes the formation of a covalent phosphodiester bond between the $3'\text{-OH}$ end of one nucleotide and the $5'\text{-phosphate}$ end of another, sealing single-strand nicks in double-stranded DNA.
• Polymerases synthesize nucleic acid polymers from monomers; Helicase unwinds double-stranded DNA.

Option analysis:
(A) Econometric models (time-series, cross-sectional, and panel regressions) are statistical/empirical modeling tools, whereas mechanistic crop simulation models (e.g. DSSAT, CERES, APSIM) simulate dynamic biological and physical processes.

Etiology of wheat ear cockle:

• Ear cockle (also known as seed gall disease of wheat) is caused by the seed gall nematode, Anguina tritici.
• Second-stage juveniles infect floral tissues, transforming normal grains into dark, hardened nematode galls (cockles).
• When associated with the bacterium Rathayibacter tritici, it causes yellow ear rot or 'Tundu' disease.