The correct option is C Fresh water
Spirogyra are found in fresh water such as pools, ponds, lakes, ditches etc. and also in slow running water of rivers and streams. They occur as free floating bright green masses in the water but few species such as spirogyra dubia, spirogyra affinis, spirogyra rhijoides develop specialized structure hapteron with the help of which they can get attached with substratum.