Final answer:
Option A (mZDEB = mBD + mAC) is the correct relationship derived from simplifying the given equation 2(m_DEB) = mBD + mAC.
Step-by-step explanation:
The given equation is 2(m_DEB) = mBD + mAC. To find which relationship is true, we need to simplify and interpret the given equation. Since the equation consists of measure of angles and their relationships, we can presume that m_DEB stands for the measure of angle DEB in a geometrical context. Therefore, by simplifying, we can deduce that mZDEB equals to 2 times m_DEB. The equation simplifies to mZDEB = mBD + mAC, which matches option A. Therefore, option A (mZDEB = mBD + mAC) is the correct relationship that is true according to the given equation.