In which group are the cell walls typically made up of two interlocking parts known as the epitheca and hypotheca?

Explanation

The cell wall structure consisting of two overlapping halves, the epitheca (upper half) and hypotheca (lower half), is characteristic of diatoms (option A). This unique feature distinguishes them from other groups such as desmids, dinoflagellates (Pyrrophyta), and green algae (Chlorophyta).