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Assuming the sun to have a spherical out...

Assuming the sun to have a spherical outer surface of radiating like a black body at temperature `t^@C`, the power received by a unit surface,(normal to the incident rays) at a distance R from the centre of the sun is

A

`r^2sigma (t + 273)^4//R^2`

B

`4pir^2sigmat^4//R^2`

C

`r^2sigma (t+ 273)^4//4piR^2`

D

`16pi^2r^2sigmat^4//R^2`

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