Which of the following substances is an element? A. water B. table salt C. iron oxide D. hydrogen

Explanation:

An element has a uniform composition, cannot be broken down by chemical change, every atom has the same atomic number, and can be found on the Periodic Table.

Water is made of hydrogen and oxygen atoms (H₂O) so it is not an element.

Table salt is made of sodium and chloride atoms (NaCl) so it is not an element.

Iron oxide is made up of iron and oxygen atoms, so it is not an element.

Hydrogen is an element. It can be found on the Periodic Table as element H.

The correct answer is D. Hydrogen

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.

there are two significant figures.