Explain how you know when to combine terms with veriables

The correct answer is c

The median segment divides the triangle into 2 isosceles triangles and everything else is trivial.|ad|=|bc|2=|bd|soδadb  is isosceles with∠dab=∠dbasimilarlyδadc  is isosceles with  ∠dac=∠dca∠cab=∠cad+∠bad=∠acb+∠abctherefore∠cab  is a right angleandbc  is the hypotenuse of a right-angled triangle.hope this