Answer:
Option B is true
Explanation:
We are given that three right triangles .Triangles ABD,CAD and CBA are similar.
When two triangles are similar then, the corresponding sidea are in equal proportion.
We have AB=5 units
AC= 7 units
BC=x
Triangles ABD is similar triangle CBA




When triangle CAD and CBA are similar
Then,




In traingle CBA, uisng pythagoras theorem




Hence, option B is true.