The correct answer is option 'C', which states that the temperature of the measurement is a comparatively insignificant factor affecting the magnitude of specific optical rotation.

Explanation:

Specific optical rotation is a property of chiral molecules that describes the extent to which they rotate the plane of polarized light. It is given by the equation:

\[ \alpha = \frac{{\alpha}}{{c \cdot l}} \]

where:
- α is the observed rotation in degrees,
- c is the concentration of the substance in g/mL,
- l is the length of the sample tube in dm.

The factors that can affect the magnitude of specific optical rotation include:
a) Concentration of the substance of interest: The concentration of the substance can affect the observed rotation. According to the equation, as the concentration increases, the observed rotation also increases. Therefore, the concentration is a significant factor affecting the magnitude of specific optical rotation.

b) Purity of the sample: The purity of the sample is another important factor. Impurities in the sample can interfere with the rotation of polarized light, leading to inaccurate measurements. Therefore, the purity of the sample is a significant factor affecting the magnitude of specific optical rotation.

c) Temperature of the measurement: The temperature of the measurement, on the other hand, has a comparatively insignificant effect on the magnitude of specific optical rotation. While temperature can affect the physical properties of the sample, such as its density, it does not directly affect the rotation of polarized light. Therefore, the temperature is a comparatively insignificant factor affecting the magnitude of specific optical rotation.

d) Length of the sample tube: The length of the sample tube is also a significant factor affecting the magnitude of specific optical rotation. According to the equation, as the length of the sample tube increases, the observed rotation decreases. Therefore, the length of the sample tube is a significant factor affecting the magnitude of specific optical rotation.

In conclusion, out of the given options, the temperature of the measurement is the comparatively insignificant factor affecting the magnitude of specific optical rotation.