Choose the correct statement regarding the design concepts of proportion and scale.
a. The terms proportion and scale are interchangeable terms when used in design. They both refer to size in relation to other objects.
b. Proportion refers to the dimensions of objects in a group; scale refers to the dimensions of groups in a room.
c. Proportion refers to the object's size in relation to other objects; scale refers to the object's measured dimensions.
d. Proportion has to do with the sizes of the parts of an object; scale refers to the size of an object in relation to the size of other objects.