Solution:
Statement I: Boron is extremely hard indicating its high lattice energy.
Boron forms a giant covalent structure rather than an ionic lattice. Its hardness is due to its strong covalent network, not high lattice energy. Therefore, Statement I is incorrect.
Statement II: Boron has the highest melting and boiling point compared to its other group members.
Boron has a very high melting and boiling point due to its strong covalent network structure. This is true compared to the other group 13 elements. Therefore, Statement II is correct.
Therefore, Statement I is incorrect but Statement II is correct.
Correct Answer: (1) Statement I is incorrect but Statement II is correct