The value of Stefan-Boltzmann constant in SI unit is_________________?

A. 5.6697 × 10-8W/m2.°K4
B. 0.1714 × 10-8W/m2.°K4
C. 5.6697 × 10-8kcal/m2. °K4
D. 0.1714 × 10-8kcal/m2. °K4