Vì sao con người phải tạo ra các giống câu trồng hoặc vật nuôi mới?

The double bond between a carbon atom and two oxygen atoms (a molecule of carbon dioxide) has two characteristics. what are they? a.an ionic bond is formed between the oxygen and carbon atoms. b.four valence electrons are shared. c.two valence electrons are shared. d.valence electrons are shared between oxygen atoms.

What organs comprise the respiratory system of a bird

Substances that can pass through cell membranes by diffusion include a. na ions. b. proteins c. glucose. d. oxygen.