The correct option is C 4.8cm
In a right angled triangle ,if a perpendicular is drawn from the vertex of the right angle to the hypotenuse, then the triangles on both sides of the perpendicular are similar to the whole triangle and to each other.
Consider ΔBCA and ΔCDA
∠A = ∠A (common angles)
∠BCA=∠CDA (Right angles)
∴ΔBCA∼ΔCDA
→BCCD=ABAC
→6x=108
→x=4810=4.8cm