Which of the following statements is NOT true for a homologous series?
Correct: D
A homologous series is a series of organic compounds in which all members have the same functional group and similar chemical properties (not identical, but similar due to the same functional group). They differ by a -CH2 unit, have the same general formula, and show a gradual change in physical properties as molecular mass increases. Statement D is incorrect because having different functional groups would mean they are not part of the same homologous series and would lead to different chemical properties.