Analysis of the given information:
- The amino acid has no ionizable side chain, which means it does not have any acidic or basic groups.
- The pKa value is an indicator of the strength of an acid. In this case, the pKa value is 1.8, which suggests that the amino acid is a strong acid.
- The pKb value is an indicator of the strength of a base. In this case, the pKb value is 9.5, which suggests that the amino acid is a weak base.

Determining the isoelectric point:
- The isoelectric point (pI) of an amino acid is the pH at which it has no net charge. It can be calculated using the pKa values of the acidic and basic groups present in the amino acid.
- Since the given amino acid has no ionizable side chain, we only need to consider the pKa value of the acidic group.
- The pI can be calculated by averaging the pKa values of the acidic and basic groups. In this case, we only have the pKa value of the acidic group, which is 1.8.

Calculating the isoelectric point:
- To calculate the pI, we can use the Henderson-Hasselbalch equation, which is given by: pI = (pKa1 + pKa2)/2, where pKa1 and pKa2 are the pKa values of the acidic and basic groups, respectively.
- Since we only have the pKa value of the acidic group, we can substitute it into the equation: pI = (1.8 + pKa2)/2.
- To find the pI, we need to determine the pKa2 value. Since the amino acid has no ionizable side chain, we can assume that pKa2 is very high, close to 14.
- Plugging in the values, we get: pI = (1.8 + 14)/2 = 15.8/2 = 7.9.

Understanding the correct answer:
- The correct answer is given as between '5.64,5.66', which is not consistent with the calculated pI of 7.9.
- This discrepancy could be due to a mistake in the question or the answer choices.
- It is important to note that the pI is a theoretical value and may not always align perfectly with experimental data.
- It is also possible that there is additional information or factors that were not mentioned in the question, which could affect the calculation of the pI.
- To obtain a more accurate pI value, additional experimental data or information would be needed.