Highest melting point among the following is displayed by

$(a)$ Give reactivity of alkaline earth metals towards air,water,dihydrogen and acids.
$(b)$ Explain reducing nature of alkaline earth metals.
$(c)$ Give chemical reaction of alkaline earth metals with liquid ammonia.

How would you explain the following observations?
$(i)$ $BeO$ is almost insoluble but $BeSO_4$ is soluble in water,
$(ii)$ $BaO$ is soluble but $BaSO_4$ is insoluble in water,
$(iii)$ $LiI$ is more soluble than $KI$ in ethanol.

Match the following:

Metal	Uses
$1. \text{Be}$	$c. \text{To prepare windows of X-rays}$
$2. \text{Ca}$	$d. \text{To remove air from vacuumized tubes}$
$3. \text{Mg}$	$a. \text{To prepare Grignard reagent}$

Beryllium shows a diagonal relationship with aluminum. Which of the following similarities is incorrect?

What happens when:
$(i)$ Magnesium is burnt in air
$(ii)$ Quick lime is heated with silica
$(iii)$ Chlorine reacts with slaked lime
$(iv)$ Calcium nitrate is heated?