Which of the following statements is/are true?
I. When two or more compounds have similar molecular formula, but different carbon skeletons, they are referred as chain isomers.
II. When two or more compounds differ in the position of substituent atom or functional group on the carbon skeleton, they are called functional isomers.
III. The isomerism, which arises due to the presence of different alkyl chains on either side of the functional group in the molecule is referred to as metamerism.