Why do we perceive objects as retaining their brightness under different lighting levels?

Which of the following happened during the precambrian era? the first prokaryotic cells the first eukaryotic cells development of photosynthesis all of the above

Adescription of a type of bio biotechnology (genetic engineering, cloning, or artificial section) one benefit or one risk for the individual (based on whether you are for or against it) one benefit or one risk for society (based on whether you are for or against it) one benefit or one risk for the environment (based on whether you are for or against it)

Are the layers of rock above and below the coal older or younger?