In which of the following is a metal-to-metal bond present?

Present a comparative account of the alkali and alkaline earth metals with respect to the following characteristics :
$(a)$ Tendency to form ionic/covalent compounds.
$(b)$ Nature of oxides and their solubility in water.
$(c)$ Formation of oxosalts.
$(d)$ Solubility of oxosalts.
$(e)$ Thermal stability of oxosalts.

Which of the following electronic configurations belongs to $s-$block elements?

The metal that gives hydrogen gas upon treatment with both acid as well as base is

'Bordeaux mixture' is used as a fungicide. It is a mixture of

Which of the following substances is used as a fertilizer?