[单选题]
The average radius of Neptune's (a(g)+ri.uko l mhy9oorbit around the Sun is approximately 30 ti/vsy:xl( + otgoy :qijm 3y4h7mes the orbital radius of earth. Estimate jyh7qltv +xy3gi:y: /so(o4m the solar constant of Neptune.
A. 1.5$Wm^{-2}$
B. 23$Wm^{-2}$
C. 45$Wm^{-2}$
D. 1360$Wm^{-2}$