Has the SI metric system been declared the preferred system of measurement by the United States Congress?

The correct answer is that the SI metric system has indeed been recognized by the United States Congress as the preferred system of measurement. This recognition is rooted in the Metric Conversion Act of 1975, which encouraged the use of the metric system in the United States. While it wasn't mandated for total adoption, the act acknowledged the benefits of metric measurements and promoted their use in various sectors, particularly in science, industry, and commerce.

This perspective has been reinforced over the years, as various government agencies and sectors have increasingly adopted the SI metric system for its clarity, precision, and international standardization, which facilitates trade and communication. Thus, citing the declaration by Congress reflects the ongoing support for the metric system, even as customary units are still prevalent in everyday usage.