24. 蝴蝶产卵
Upon maturity,monarch butterflies travel hundreds of miles from their places of origin and lay their eggs on milkweed. The caterpillars that emerge feed on milkweed and absorb the glycosides in milkweed sap. The specific glycosides present in milkweed differ from region to region within the monarch butterflys range. Mature butterflies retain the glycosides in a mature monarch butterfly could be used to determine its place of origin.
Which of the following, if true, most strengthens the argument?
A. Mature monarch butterflies do not feed on parts of milkweed that contain glycosides.
B. The glycosides in milkweed sap are slightly toxic to caterpillars of other species.
C. The vast majority of the monarch butterflies that are laying eggs in a given region will have traveled there from a single region.
D. There are substances other than glycosides in milkweed sap that accumulate in a monarch caterpillar and are retained in the body of the mature butterfly.
E. There are certain glycosides that are found in the sap of all milkweeds, no matter where they grow within the monarch butterflys range.
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