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Best answer

$\underbrace{4^{2}}_{\text{Size 1 unit}} + \underbrace{3^{2}}_{\text{Size 2 unit}} + \underbrace{2^{2}}_{\text{Size 3 unit}} + \underbrace{1^{2}}_{\text{Size 4 unit}} = 16 + 9 + 4 + 1 = 30$

$\textbf{Note:}\; 1^{2} + 2^{2} + 3^{2} + \dots + n^{2} = \dfrac{n(n+1)(2n+1)}{6}.$

So, the correct answer is $(B).$

$\textbf{Note:}\; 1^{2} + 2^{2} + 3^{2} + \dots + n^{2} = \dfrac{n(n+1)(2n+1)}{6}.$

So, the correct answer is $(B).$