Which of the answer choices correctly describes covalent bonds?

a) an attraction between oppositely charged ions
b) a force that holds atoms or ions together in a fixed structure or unit
c) a sharing of four pairs (eight valence electrons) between two atoms
d) a sharing of an electrons pair between two atoms

The drag force, fd, imposed by the surrounding air on a vehicle moving with velocity v is given by fd = cdaρv 2/2 where cd is a constant called the drag coefficient, a is the projected frontal area of the vehicle, and ρ is the air density. an automobile is moving at v = 80 kilometers per hour with cd = 0.28, a = 2.3 m2, and ρ = 1.2 kg/m3.