And projects like Ibream are also looking at the possibility of cloning rhinos, as a weapon of last resort if this species plummets further.

类似Ibream这样的项目同时也在寻求克隆犀牛的可能性，如果这一物种进一步锐减，克隆将成为最后的杀手锏。

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Still more dangerously, by treating nuclear weapons as just another explosive in the arsenal, rather than as a deterrent weapon of last resort, America would dangerously blur the line against nuclear use by anyone.

ECONOMIST: Why some weapons are best left unexplored

"The way Syria configured its chemical arsenal was essentially as a weapon of strategic deterrence, not really to be used on the battlefield, but as an instrument of last resort, " said Mr. Zanders of the EU Institute, likening Syria's capacity to use chemical weapons to how Israel treats its nuclear weapons.

WSJ: Syria Chemical Report Spurs Probes, Theories