Final answer:
The nucleic acids that assist in protein synthesis and are single-stranded polymers include mRNA, which is a transcript of DNA carrying information for constructing proteins.
Step-by-step explanation:
Nucleic acids which assist in the production of proteins and are normally found as a single-stranded polymer include d) mRNA. Messenger RNA, or mRNA, is a single-stranded transcript of DNA that is crucial for protein synthesis. Unlike DNA, which is a double-helical structure, RNA is single-stranded and includes not only mRNA but also rRNA (ribosomal RNA), tRNA (transfer RNA), and miRNA (microRNA). rRNA is a component of ribosomes, tRNA transfers specific amino acids to a developing protein chain during translation, and miRNA regulates the expression of mRNA strands.