Which of the following statements regarding demographic transition theory are true?
\[
\begin{aligned}
A.&\ \text{There were three distinct parts of the theory--descriptive, theoretical and predictive.}
B.&\ \text{Originally, the theory was given by Thompson.}
C.&\ \text{It is based upon the trends in mortality, fertility and natural increase in less developed countries of the world.}
D.&\ \text{It postulates a particular pattern of demographic change from a high fertility and high mortality to a low fertility and low mortality.}
\end{aligned}
\]
Choose the correct answer from the options given below: