Answer :
The projections that are released to protect its body from the acid are trichocysts. These trichocysts are released for the self-defense of the paramecium.
Answer is a. he projections are trichocysts, released for the self-defense of the Paramecium.
When Paramecium is stimulated by chemicals such as picric acid or an injurious enemy, it responds by throwing out transparent spine-like projections called trichocysts. The discharge of trichocysts forms an effective barrier round the animal and protects it from acid or enemy.