Final answer:
The existence of different racial categories in Brazil that do not have equivalents in the United States suggests that race is a social construct, not a fixed or scientific classification.
Step-by-step explanation:
Race is a social construct. The existence of different racial categories in Brazil, such as moreno, mulato, neguinho, and pretinho, that do not have equivalents in the United States suggests that race is not a fixed or scientific classification, but rather a social and cultural construction. These categories are specific to the Brazilian context and reflect the country's diverse population and cultural heritage.