According to the passage, which of the following is true of an Eurasia-Africa land bridge during ice ages? A. It offers suitable habitats for cold-adapted species of antelope. B. It encourages migration from Africa to Eurasia of cold-adapted species of antelope. C. It allows the survival of warm-adapted species of antelope that might otherwise home extinct. D. It is more likely to exist early in an ice age than later in an ice age. E. The habitats it offers change more quickly than do those offered by land bridges during other periods.