Final answer:
The expression (3r - 2) is equivalent only to itself among the given options, so the correct answer is B. 3r - 2. The other options either change the variable or the constants involved.
Step-by-step explanation:
The expression (3r - 2) is equivalent to itself, which means the correct answer from the provided options would be B. The other options represent different expressions or involve a variable different from 'r'.
Let's review the options briefly:
Option A, 3r - 6: This is not equivalent because the constant term is -6 instead of -2.
Option B, 3r - 2: This is exactly the same as the original expression, so it is equivalent.
Option C, 3x + 2: This expression has a different variable and a positive constant term, so it's not equivalent.
Option D, 3r + 6: This has a positive constant term and is therefore not equivalent.