Write the name and symbol of the reference element that has been used as a standard substance to define the relative atomic mass.

Explanation

To answer the question, we need to identify the reference element used to define the relative atomic mass.

### Step-by-Step Solution:

1. **Identify the Reference Element**: The question asks for the reference element used as a standard to define relative atomic mass. The standard reference element is Carbon.

2. **Determine the Specific Isotope**: Among the isotopes of carbon, the specific isotope used is Carbon-12.

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