The correct option is
A mitochondria
Krebs cycle is the stepwise oxidative and cyclic degradation of acetyl CoA derived from pyruvate. It was discovered by Hans Krebs and occurs inside the matrix of mitochondria.
In the chloroplast, no component of cellular respiration occurs, but in C3 plants, photorespiration does occur inside chloroplasts. Glycolysis takes place in the cytoplasm. Ribosomes are known for protein synthesis.