单选题How this kind of pla

问题补充：

单选题Howthiskindofplantcanbe____inaspecialwayisstillunknowntous.A.kept awayB.kept outC.kept aliveD.kept off

答案：

C解析keep alive意为:使…活着; keep away意为:使…离开; keep out意为:不使入内,防止; keep off意为:不让接近.