Which of the following statements are true? Select all correct answers.
a. A plant that produces more monounsaturated fatty acids than polyunsaturated fatty acids in its membranes in winter has an increased resistance to freeze damage.
b. Cell membranes in cold-tolerant winter wheat plants have a higher ratio of unsaturated fatty acids to saturated fatty acids than do cold-intolerant wheat varieties.
c. Yeast cells that produce more unsaturated fatty acids than saturated fatty acids in response to cold have greater cold tolerance.
d. Cell membranes in reindeer legs (near the hooves) are kept flexible because they have a large number of saturated fatty acids.