Explanation
Prokaryotic ribosomes are composed of two subunits, one smaller than the other. The smaller subunit is called the 30S subunit and the larger subunit is called the 50S subunit. Therefore, option B, "30S and 50S," is the correct answer.
Option A, "30S and 40S," is incorrect because the 40S subunit is actually found in eukaryotic ribosomes, not prokaryotic ribosomes.
Option C, "40S and 50S," is also incorrect because this combination of subunits is found in eukaryotic ribosomes, not prokaryotic ribosomes.
Option D, "40S and 60S," is also incorrect because this combination of subunits is found in eukaryotic ribosomes, not prokaryotic ribosomes.
