Ablue solution turns yellow when it is exposed to a weak acid. a small amount of this blue solution was added to a test tube of water containing an aquatic snail. the color of the water in the tube changed from blue to yellow after 30 minutes. a possible explanation for this color change is that the

A possible explanation for this color change could be the acid present in the  Snail slime has brought the color change.

Explanation:

Snails are  Gastropod molluscs.They secrete a mucus like watery slime to adhere to the surface .Snails also use their slime as a defense.Chemical analysis of snail slime suggested that it contains hyaluronic acid and glycolic acid along with other components.Thus we can state that snail slime is acidic in nature.In the given question it is stated that the blue solution turns yellow on adding a weak acid. So when the color of water changed from blue to yellow  after 30 minutes, we can assume that the colour change was caused due to the slime secreted by Aquatic snail that was introduced into the tube.

Fungi is were it belongs