Questions

Answer D is correct because a sunk cost is a project expense that will eventualy need to be paid. Answer A is incorrect because a fixed cost remains constant, regardless of any change in a company's activity. Answer B is incorrect because direct cost can be directly linked to producing specific goods or services. Answer C is incorrect because a variable cost changes in proportion to a change in the company's activity or business.

Passivity of iron is due to formation of an extremely thin and impervious film of ferrosoferric oxide Fe3O4on the surface of iron. Chromic acid, being a powerful oxidising agent (like nitric acid ) renders iron passive. 

A tetrad is best described by Four chromatids. It is formed from two homologous chromosomes, each consisting of two chromatids in the first stage of meiosis called prophase1.