Answer: C
Step-by-step explanation:
Using the Triangle Inequality Theorem, the sum of two sides must be greater than the third side.
BD + DC > BC and DC + BC > BD and BD + BC > DC
x+3 + DC > 9 and DC + 9 > x+3 and x+3 + 9 > DC
-3 -3
DC + 6 > x
x < DC + 6
If x + 3 + DC > 9, then obviously x + 3 > 9
Similarly, if x < DC + 6, then obviously x < 6
