The stain used to visualise mitochondria is
1. fast green
2. safranin
3. acetocarmine
4. janus green

(d) Janus  green is used to stain mitochondria. Janus green act as an indicator and changes colour according to the amount of oxygen present. It oxidizes to blue colour in presence of oxygen and in its absence changes and its colour to pink.
Safranin is used to stain nuclei and lignified walls of cell.
 Acetocarmine  is used for Staining nucleic acid and chromosomes.
Fast green It is used for Staining histones at alkaline pH after acid extraction from DNA.