Which radioactive isotope is commonly used to date wooden artifacts?
A. potassium-40 (40k)
B. potassium-40 ( 40 k)
C. argon-38 (38ar)
D. argon-38 ( 38 ar)
E. uranium-238 (238u)
F. uranium-238 ( 238 u)
G. carbon-14 (14c)