A vehicle manufacturer makes base models using a large$-$scale production process. It also partners with small companies that help customize its vehicles, thus offering a wide range of packages involving a variety of chassis colors, upholstery designs, music systems, GPS devices, and passenger safety options. The company's approach to its service offering is an example of $\_\_\_\_\_\_\_.$

a$.$

standardization

b$.$

mass standardization

c$.$

mass customization

d$.$

customization