Explanation:
The correct option is 'b'. A Tillaux fracture is an avulsion fracture of the anterolateral distal tibial epiphysis. It occurs in adolescents (usually 12-14 years old) because the distal tibial physis closes from central to anteromedial to posteromedial, and finally anterolateral. External rotation force causes the anterior inferior tibiofibular ligament (AITFL) to avulse the unfused anterolateral fragment (Salter-Harris III).

Reference: Horn BD, et al. Radiographic evaluation of juvenile tillaux fractures of the distal tibia. J Pediatr Orthop. 2001;21(2):162-164.