From the statements given below choose the correct option :

A.   The eukaryotic ribosomes are 80S and prokaryotic ribosomes are 70S.

B.   Each ribosome has two sub-units.

C.   The two sub-units of 80S ribosome are 60S and 40S while that of 70S are 50S and 30S.

D.   The two sub-units of 80S ribosome are 60S and 20S and that of 70S are 50S and 20S.

E.    The two sub-units of 80S are 60S and 30S and that of 70S are 50S and 30S.

To determine which of the given statements about ribosomes are correct, we review the established facts about ribosomal structure in eukaryotes and prokaryotes.

Statement A: “The eukaryotic ribosomes are 80S and prokaryotic ribosomes are 70S.”

In cellular biology, ribosome size is expressed in Svedberg units (S), which reflect sedimentation rate during ultracentrifugation. Eukaryotic cytoplasmic ribosomes sediment at 80S, consisting of a large 60S subunit and a small 40S subunit. Prokaryotic ribosomes sediment at 70S, composed of a large 50S subunit and a small 30S subunit. Therefore, Statement A accurately describes the S values for the two domains of life.

Statement B: “Each ribosome has two sub‑units.”

All functional ribosomes are heteromeric complexes formed from two distinct sub‑units: a large sub‑unit that catalyzes peptide bond formation and a small sub‑unit that binds messenger RNA and initiates translation. This applies to both the 80S eukaryotic ribosome and the 70S prokaryotic ribosome. Hence, Statement B is correct.

Statement C: “The two sub‑units of 80S ribosome are 60S and 40S while that of 70S are 50S and 30S.”

Combining the information from Statements A and B, the specific sub‑unit sizes are well‑known: the eukaryotic 80S ribosome comprises a 60S large sub‑unit and a 40S small sub‑unit; the prokaryotic 70S ribosome comprises a 50S large sub‑unit and a 30S small sub‑unit. This matches the description in Statement C, making it true.

Now we briefly address why the remaining statements are false:

Statement D: “The two sub‑units of 80S ribosome are 60S and 20S and that of 70S are 50S and 20S.”

The small sub‑unit of the eukaryotic ribosome is 40S, not 20S, and the small sub‑unit of the prokaryotic ribosome is 30S, not 20S. Therefore, Statement D is incorrect.

Statement E: “The two sub‑units of 80S are 60S and 30S and that of 70S are 50S and 30S.”

The eukaryotic small sub‑unit is 40S, not 30S. Thus, Statement E misstates the eukaryotic sub‑unit composition and is false.

In summary, the only statements that accurately reflect ribosomal biology are A, B, and C. Hence the correct option is “A, B, C are true.”