Answer:
A) Q + XZ = X + QZ is a single displacement reaction. 
B) Q + Z = QZ is a synthesis reaction 
C) QT = Q + T is a decomposition reaction 
D) QT + XZ = QZ + XT is double replacement reaction. 
Step-by-step explanation:
A) Q + XZ = X + QZ
This is a single displacement reaction because it is one in which one element is substituted for another one in a compound. In this case X is substituted for Q.
B) Q + Z = QZ
This is a synthesis reaction because Q and z combine to form a single product QZ.
C) QT = Q + T
This is a decomposition reaction because the compound QT breaks down to form 2 simpler substances Q and T.
D) QT + XZ = QZ + XT
Thus is a double replacement reaction because QT and XZ have exchanged cations to form new compounds QZ and XT