The specific rotation of a compound is defined as the observed rotation of the compound when its concentration is 1 g/mL in a sample tube which is 10 cm long. If a certain compound is observed to have a specific rotation of +8.0°, what rotation will be observed if the sample concentration is 0.25 g/mL and the sample tube is 20 cm long?
A. +2°
B. +4°
C. +16°
D. +32°