That's "insolation" ... not "insulation".
'Insolation' is simply the intensity of solar radiation over some area.
If 200 kW of radiation is shining on 300 m² of area, then the insolation is
(200 kW) / (300 m²) = (666 and 2/3) watt/m² .
Note that this is the intensity of the incident radiation. It doesn't say anything
about how much soaks in or how much bounces off.
Wait !
I just looked back at the choices, and realized that I didn't answer the question
at all. I have no idea what "1 sun" means. Forgive me. I have stolen your
points, and I am filled with remorse.
Wait again !
I found it, through literally several seconds of online research.
1 sun = 1 kW/m².
So 2/3 of a kW per m² = 2/3 of 1 sun
That's between 0.5 sun and 1.0 sun.
I feel better now, and plus, I learned something.