Which of the following statements is not consistent with Kant’s concept of the categorical imperative?

(a) Act only according to that maxim by which you can at the same time will that it should become a universal law.

(b) In some circumstances, the end justifies the means.

(c) Always treat persons as an end and never as a means.

(d) Act according to a maxim that harmonizes with a possible realm (i.e., a systematic union of different rational beings through common laws).