The answer is choice C 50%
The correct answer is mRNA.
mRNA or messenger RNA is synthesized during the process of transcription, from DNA molecule which is used as a template. mRNA contains information about protein synthesis (translation) in the form of nucleotide triplets or codons.
In the example above: reference book is DNA molecule (template for copies), copies are mRNA, wood is amino acids (building blocks) and doghouse is protein.
The answer to this question would be Ronchi.
Ronchi is low-pitch sound from lungs that might be caused when there are liquid inside the alveolus. That is why the sound might be disappeared after the patient coughing as it can remove the liquid. Ronchi is common is pneumonia/lung infection patient.
Others lung sound with high-pitch would be called wheezing, which common in asthma.