The correct answer is: C. constant returns to scale
Constant returns to scale means that if all inputs are increased by a certain percentage, then output will also increase by the same percentage. In this case, if we double the amount of labor and capital, we will also double the amount of output.
Increasing returns to scale means that if all inputs are increased by a certain percentage, then output will increase by more than that percentage. In this case, if we double the amount of labor and capital, we would get more than double the amount of output.
Decreasing returns to scale means that if all inputs are increased by a certain percentage, then output will increase by less than that percentage. In this case, if we double the amount of labor and capital, we would get less than double the amount of output.
The data in the question shows that when we double the amount of labor and capital, we also double the amount of output. This means that the production technology satisfies constant returns to scale.