If potentially hazardous foods are in "the danger zone," they can become unsafe in 4 hours
20 minutes
2 hours
40 minutes

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of carbon is as shown here in the image.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.