Predicting the vitamin d status of a person based on sun exposure is difficult because of

The correct answer is a time of the day, latitude and season.

There are numerous factors that minimize the production of skin's Vitamin D3, including aging, increased pigmentation of the skin, and the topical application of a sunscreen.

A change in the zenith angle of the sun resulting due to a change in a season of the year, latitude, or time of the day drastically affects the production of skin's Vitamin D3. So, it is tough to determine the levels of vitamin D3 on the basis of the exposure of the sun.

i think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.