The declaration $\_\_\_\_\_$ indicates that the primary font that the browser tries to use is the Cambria font.

a$.$

font$-$family: $<$"Times New Roman", "serif"$>$ Cambria;

b$.$

font$-$family: pr$,$ "Times New Roman", serif;

c$.$

font$-$family: Cambria, "Times New Roman", serif;

d$.$

font$-$family: "serif", Times New Roman, Cambria;