Question

question 4
which of the following is an element?
sucrose
sodium chloride
hydrogen gas
question 5
which of the following is not one of the four most common elements?
sodium
oxygen
nitrogen
hydrogen
carbon

Explanation:

• For Question 4: An element is a pure substance made of only one type of atom. Sucrose is a compound ($C_{12}H_{22}O_{11}$), sodium - chloride is a compound ($NaCl$), and hydrogen gas ($H_2$) is made of only hydrogen atoms, so it is an element.
• For Question 5: The four most common elements in living things are carbon, hydrogen, oxygen, and nitrogen. Sodium is not one of them.

Answer:

Question 4: C. hydrogen gas
Question 5: A. Sodium