Select the option that is a correct equation for the horizontal coordinate of the projectile as a function of time.
a) x = v0 * t + (1/2) * a * t²
b) x = v0 * cos(θ) * t
c) x = v0 * sin(θ) * t + (1/2) * a * t²
d) x = v0 * cos(θ) * t + (1/2) * a * t²