In what cell types is telomerase active?

Telomerase is active in gametes and most cancer cells, but is normally absent from, or at very low levels in, most somatic cells.

Decomposition:
A compound partitions into its components.
Try to look at the word itself: DECOMPOSITION. When you put components to create the whole new thing, you compose (music from notes, dinner from ingredients etc.). To decompose is the opposite process.