Pumas never attack a human being except( )cornered?

Pumas never attack a human being except( )cornered? Pumas never attack a human being except( )cornered?选项：A they Pumas never attack a human being except( )cornered?这新概念的老问题哈 pumas never attack a human being except ___cornered. Pumas never attack ahuman being except being cornered.这句话哪里有 Pumas never attack a human being except when the are cornere pumas never attack a human being expect _____cornered.A.they Pumas never attack a human being except_____conered. A.that only when it is hungry will a lion attack a human being. 英语的虚拟语态新概念第三册第一课就有一个句型:a puma will not attack a human being a human being a human kind human,human being