Step 1: Understanding the elements in the list
Pasteurization (A): Cork screw shaped bacteria (i).
Bacillus spp (B): Feeds on organic detritus (iv).
Spirochaetes (C): DNA components to detect active toxic pollutants (ii).
Biosensors (D): Mild heating of milk to kill particular pathogens (iii).
Final Answer:
A-i, B-iv, C-ii, D-iii