What are the advantages and limitations of the PCR technique?
a. The PCR technique can be completed in hours, can be applied to a wider range of tissues, requires less DNA or RNA, and has great versatility.
b. The sensitivity of the PCR technique is limited by the degradation of DNA or RNA, and contamination is a major technical issue.
c. The PCR technique only analyzes the chromosomal region flanked by the primers used, and does not review the entire genome.
d. The RT-PCR technique only analyzes the mRNA and does not provide information on the presence of mutations or the transcription level of other related genes.

a, b, c, and d are correct.
a and c are correct.
b and d are correct.
Only a is correct.