The following table, which is part of a wider question, apparently shows constant returns to scale. My calculations do not seem to show that constant returns to scale occurs.
The correct answer is B.
I can find at least 2 sources claiming that returns to scale occurs when a same change in inputs results in the same quantity change in output
If output increases by that same proportional change as all inputs change then there are constant returns to scale (CRS).
Constant returns to scale occurs when increasing the number of inputs leads to an equivalent increase in the output.