Segmentation in the body is first observed in which of the following: (a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda

(c) Annelida. Segmentation, also known as metamerism, is first observed in phylum Annelida where the body is divided into repeating segments both externally and internally, which allows for greater flexibility and complexity in movement and function.