The mismatch is: Template — double-stranded DNA. In PCR, the template used for synthesis is single-stranded DNA (after denaturation). The original dsDNA is denatured to single strands first, and each single strand serves as the template for new strand synthesis. The Taq polymerase (thermostable, from Thermus aquaticus), primers (short oligonucleotides), and 5′→3′ synthesis direction are all correct PCR components and descriptions.