Step 1: Recall the concept of Social Welfare Function (SWF).
A Social Welfare Function aggregates the utilities of all individuals in society into a single measure of social welfare.
\[
SWF=f(U_1,U_2,\ldots,U_m)
\]
Step 2: Analyze option (A).
The classical utilitarian approach associated with Jeremy Bentham and John Stuart Mill gives equal importance to individuals.
The standard utilitarian SWF is
\[
SWF=\sum_{i=1}^{m}U_i
\]
and not a weighted sum with unequal weights.
Therefore, option (A) is incorrect.
Step 3: Analyze option (B).
Interpersonal comparisons in welfare economics involve normative value judgements and cannot be made purely on objective scientific grounds.
Hence, option (B) is incorrect.
Step 4: Analyze option (C).
John Rawls proposed the
maximin criterion, not the maximization of the maximum utility.
Rawlsian SWF is
\[
SWF=\min\{U_1,U_2,\ldots,U_m\}
\]
which focuses on maximizing the welfare of the least advantaged person.
Thus, option (C) is incorrect.
Step 5: Analyze option (D).
The utilitarian social welfare function is given by
\[
SWF=\sum_{i=1}^{m}U_i
\]
which simply sums individual utilities.
Therefore, option (D) is correct.
Step 6: Final conclusion.
Hence, the correct statement is
\[
\boxed{SWF=\sum_{i=1}^{m}U_i \text{ is the utilitarian function}}
\]
Thus, the correct option is (D).