Look at the diagram above. what is part of the arch’s anatomy is (a) labeling? a. impost c. keystone b. springing line d. voussoir

Assuming this is the image you are referring to, the correct answer would be C. keystone.
Keystone, aka capstone, is the final stone that is added to an arch in order to lock all the stones together, so that nothing will fall apart. An impost is found in the middle of a column, and it is labeled C in this diagram. Springing line is the line where the arch starts "arching." And voussoir is the stone used to make this arch - labelled B in your diagram.

To let it have a splended look