The correct option is C Ribosomes
Ribosomes were discovered by Robinson and Brown (1953) in plant cell and by George Palade (1955) in animal cell hence were called Palade particles.
In 1955 George Palade discovered previously unknown organelles in the cell, as Palade particles where the cell's formation of proteins takes place.
Later renamed ribosomes, and are now well known as the sites of protein synthesis. Hence, "Palade particles" are Ribosomes.
So, the correct answer is 'Ribosomes'.