Which compound was abundant in Precambrian Earth’s oceans, before complex life evolved on Earth? A. dissolved oxygen
B. dissolved carbon dioxide
C. dissolved methane
D. dissolved ammonia

Astairway has 6 steps. is it a handrail required? a. a handrail is required b. a handrail is not required c. double handrails are required d. only nosing is required

Select two risk factors for self-harming behavior. a. having high self-esteem b being a teenager or young adult c. being female d. having never abused drugs or alcohol i know its going to be something funny and i'm gonna feel dumb asking it but its for my final test of the semester

Which of the following could use reverse transcriptase to transcribe its genome? a) ssrnab) dsrnac) ssdnad) dsdna