Answer:
B. Two angles are a linear pair if and only if they share a side and a vertex and are supplementary.
Step-by-step explanation:
We are given that the figures representing linear pair.
From the figure, we see that,
Both the angles in a linear pair share the same vertex.
Both the angles in a linear pair share the same side.
Also, The sum of the angles in a linear pair is 180° i.e. they are supplementary angles.
That is, the correct definition for the linear pair is given by,
B. Two angles are a linear pair if and only if they share a side and a vertex and are supplementary.