Water is a________?
Methane is a_______?
A. Compound, element
B. Element, mixture
C. Element, compound
D. Compound, compound

Hint: In a mixture all the substances retain their individual properties while in a compound substances react chemically.

Complete answer:
Compounds are the substances which contain atoms of at least two elements chemically combined and the two common types of bond exist in it are covalent bond and ionic bond.
Element is defined as a substance which is made up of one type of atom for example element hydrogen which is made from atoms which consists of single proton and single electron.
Mixture is defined as a substance made by combining two or more different materials such that no chemical reaction takes place between them hence mixture can be separated back into its original components.
Therefore water is a compound and methane is also a compound as compounds are the substances which contain atoms of at least two elements chemically combined.
Water is a compound having molecular formula ${{\text{H}}_2}{\text{O}}$ and it is made up of more than one element i.e. it consists of one oxygen atom and two hydrogen atoms.
It is formed when a hydrogen ion reacts with a hydroxide ion:
${{\text{H}}^ + } + {\text{O}}{{\text{H}}^ - } \to {{\text{H}}_2}{\text{O}}$
Methane is also a compound which has a molecular formula ${\text{C}}{{\text{H}}_4}$ consisting of two different elements i.e. carbon atom and hydrogen atom, each gas molecule of compound methane is made up of one carbon atom and four hydrogen atoms, methane is basically known as a organic compound.
Hence the correct option is D.
Note: Compounds are basically of four types, first is molecules bonded together by covalent bond(sharing of electrons between them), second is when molecules bonded by ionic bonds(accepting and donating of electrons between them), third is intermetallic compounds in which they are bonded together by metallic bond and fourth is certain complexes in which coordinate covalent bond exists.