A farmer adds Azotobacter culture to soll before sowing maize. Which mineral element is being replenished?

Which of the following statements are true? i) Elements which are least reactive occur in free state or native state ii) Earthly or undesired materials present along with ore are called gangue iii) Among metals, aluminium is the most abundant in the earth crust iv) All ores are minerals but all minerals are not ores v) Gemstone "Ruby" is the impure form of Al_2O_3 containing impurity : Co vi) The set of d-block elements Cu, Ag, Au mostly occur as sulphide ore

This question contains two statements: Statement 1 and Statement 2. This question has four alternative choices, only one of which is the correct answer. Statement 1 : The reaction of aldehydes and ketones with pure HCN is very slow to yield cyanohydrin. Statement 2 : The above reaction is catalysed by a base and generated cyanide ion being a weaker nucleophile adds to carbonyl compounds to yield, corresponding cyanohydrin.

The sum of 2n terms of a series of which every even term is a times the term before it, and every odd term is c times the term before it, the first term being unity is