The correct statement is

Question

Accepted Answer

B. 1. Recall that the **valence orbitals** of an atom are all the orbitals in its outermost shell that are available for bonding; use this to check option A.
Given aluminium (Al) has one $3s$, three $3p$, and five $3d$ orbitals available in its valence shell,
$$
	ext{Total valence orbitals of Al} = 1(3s) + 3(3p) + 5(3d) = 9
$$
So option A, which states five valence orbitals, is incorrect.

2. Apply the same idea to beryllium, whose valence shell is the second shell containing only $s$ and $p$ orbitals.
$$
	ext{Total valence orbitals of Be} = 1(2s) + 3(2p) = 4
$$
Hence, option C is incorrect since beryllium actually has four valence orbitals, not three.

3. Recall that **maximum covalency** depends on the number of orbitals an atom can use for bonding, including any accessible vacant $d$-orbitals; check magnesium.
$$
	ext{Maximum covalency of Mg} = 6
$$
So option D is incorrect.

4. For boron, since its valence shell (second shell) has no $d$-orbitals, its maximum covalency is limited by the available $2s$ and $2p$ orbitals, allowing it to form up to four bonds (as seen in species like $[	ext{BF}_4]^-$).
$$
	ext{Maximum covalency of B} = 4
$$
Hence, the answer is **B**.

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