3. Compare the alkali metals and alkaline earth metals with respect to: i) Ionisation enthalpy
ii) Basicity of oxides

Alkali metals are group 1 elements while alkaline earth metals are group 2 elements.

Ionization enthalpy is the energy required to remove the most loosely bound electron from an isolated gaseous atom.   As the size decreases as we move from left to right in a period because the valence shell come closer to the nucleus as we move from left to right. Thus, the removal of electron from the valence shell becomes difficult due to greater attraction between nucleus and valence electron. Thus, the ionization enthalpy of alkaline earth metals is more than that of alkali metals.

Basicity of oxides decrease as the metallic character of the metal decreases. And as metallic character decreases on moving across a period. Basicity of oxides of alkaline earth metals is lesser than that of basicity of alkali metals.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.