Correct answer: 6m
The distance traveled in the nth second is given by the formula: \( s_n = u + \frac{1}{2}a(2n-1) \). Here, \( u = 0 \), \( a = \frac{4}{3} \), and \( n = 3 \). Substituting these values, \( s_3 = 0 + \frac{1}{2} \times \frac{4}{3} \times (2 \times 3 - 1) = 6 \, \text{m} \).