Increasing the proportion of unsaturated fatty acids in their membranes is a response of plants to（ ）.生物膜内不饱和脂肪酸比例提高可以增强植物应答（ ）。
选项：

A:Salt stress 盐胁迫;
B:Cold stress 冷胁迫;
C:Heat stress 热胁迫;
D:Water stress 水分胁迫