Which of the following, when blocks protein synthesis after mixing light and heavy ribsomes, no hybrids are formed?

Answer: Option B

Sparsomycin is an antibiotic that blocks protein synthesis by interacting with the ribosomes.

When sparsomycin is introduced into a system containing light and heavy ribosomes, it prevents the formation of hybrid ribosomes.

This occurs because sparsomycin interferes with the elongation process of protein synthesis by inhibiting the binding of aminoacyl-tRNA to the ribosome.

This inhibition prevents the formation of the necessary complexes for protein synthesis, resulting in no hybrids being formed when light and heavy ribosomes are mixed.

Therefore, the correct answer is Sparsomycin.