only on ribosome attached to the nuclear envelope and endoplasmic reticulum
on ribosome present in the nucleolus as well as in cytoplasm
on ribosomes present in cytoplasm as well as in mitochondria.
Solution
Ribosomes are known as protein factory and are actively involved in the synthesis of protein. Ribosomes are found in the cytosol and in the semi-autonomous organelles, such as mitochondria and chloroplasts.
Related Theory
Ribosomes either occur singly (monosomes) or in cluster (polysomes). Apart from ribosomal RNA (rRNA), the other two forms of RNA required for protein synthesis are: messenger $R N A$ (mRNA), which carries coding information from DNA, and transfer RNA (tRNA), which carries amino acids. Ribosomes use the information in $m R N A$ to direct the synthesis of a protein. In prokaryotes, during proteins synthesis, many ribosomes line up and join the $m R N A$ to form a string of ribosomes called polyribosome or polysome.