If cos x = p/q and 0° < x < 90°, then the value of tan x is:

• A. \(\frac{{\sqrt {{q^2} - {p^2}} }}{p}\)
• B. \(\frac{p}{{\sqrt {{p^2} - {q^2}} }}\)
• C. \(\frac{q}{{\sqrt {{q^2} - {p^2}} }}\)
• D. \(\frac{{\sqrt {{q^2} - {p^2}} }}{q}\)