The correct option is D snRNA
A polysome is a mRNA being translated into proteins by multiple ribosomes simultaneously. The mRNA is the template, rRNA is a part of the ribosome, tRNA is responsible for delivering the appropriate amino acid according to the codon sequence. All three of these RNA types are involved in the translation process.
However, snRNA, which is used for splicing is not a part of this process and hence is the correct option.