#1. another name for unicellular organisms that dominated earth up to the precambrian time is a. eukaryotes. b. cyanobacteria. c. stromatolites. d. prokaryotes. #2. the greenhouse effect is related to the phenomenon of an increase in average surface temperature known as a. air pollution. b. agricultural improvement. c. global warming. d. conservation. #3. which colorless and odorless gas, produced by radioactive decay of uranium-238, is considered to be a cancer-causing agent? a. oxygen b. hydrogen c. boron d. radon.#4. scientists can determine if oxygen existed in earth's archean atmosphere by a. determining how many people survived. b. looking for oxidized iron in rocks. c. looking at the amount of salt content in rocks. d. determining the lack of oxidation that occurred.