Albedo is a term borrowed from climatology into building science, and this question checks if you know exactly what ratio it stands for.
- Sensible Heat and Latent Heat: these two add up to give the total heat content of moist air on a psychrometric chart. They describe heat content, not surface reflectivity, so this pairing is wrong.
- Reflected Radiation and Insolation: insolation is the total solar radiation striking a surface. Some of it bounces off as reflected radiation and the rest gets absorbed. Albedo is defined exactly as reflected radiation divided by insolation, so this is the right pairing.
- Absolute Humidity and Saturation Point Humidity: dividing these gives relative humidity, a moisture measure with nothing to do with how much light a surface throws back.
- Indoor Illumination and Outdoor Illumination: this ratio is the daylight factor used in lighting design, again a different quantity from albedo.
Since albedo by definition equals the fraction of incoming solar radiation a surface sends back, the pair reflected radiation and insolation is the one that fits, so option (B) is correct.
Let's summarize:
- Albedo equals reflected radiation divided by insolation, a fraction between 0 and 1.
- Sensible/latent heat gives heat content, absolute/saturation humidity gives relative humidity, and indoor/outdoor illumination gives the daylight factor, none of these is albedo.
So albedo is the ratio between reflected radiation and insolation, option (B).