As regards the ethic principle of animal slaughter, the demand for and the number of slaughtered animals should be minimized; but for the survival and health of human beings, we have to slaughter animals, which is the evil we have to do; and necessary evils done by mankind are not, however, evils; for there is good in rational evils.

The cumene production facility revamp for Sinopec Shanghai Gaoqiao Branch is estimated from four aspects including product market, technology and policy as well as economy, the results show that the cumene production facility revamp for Sinopec Shanghai Gaoqiao Branch is necessary and feasible.

All the auxiliary verbs of necessity like yinggai (应该) can express the modality of justice and recognition.

The nature of policy and its relationship pattern with system have determined the necessity of institutional analysis of educational policy.

The necessity for power control lies in the likelihood that its character of self-dissimilation and its private property tend to combine,making it hard to control.