An element is a main constituent of paper, diamond and clothes etc. it forms covalent bonds with itself and other elements: - (1) identify the element (2) write the electron dot structure of its oxide. (3) draw the electron dot structure of methane and ethene.

Although respiratory organs vary across different organisms, they all contain respiratory surfaces that have a large surface area and are extremely thin. explain why having an extremely thin respiratory surface with a large surface area is advantageous for the process of gas exchange

The excretory system,need answers for all: )

Salt in oceans comes from and of rocks