A woman whose brother has cystic fibrosis seeks genetic counseling. She is told that she, her brother, and other family members can be tested for the common mutations known to cause this disease. DNA is obtained from her brother, and the relevant regions of the CFTR gene are amplified using a polymerase chain reaction (PCR). The DNA polymerase used in the PCR is highly resistant to which of the following?

1. A)Base
2. B)Low Ca2+ concentration
3. C)High Na+ concentration
4. D)Acid
5. E)HeatGABARITO