It remains a mystery how Theobroma cacao, which scholars believe originated in lowland Amazonia, was introduced to tropical Mesoamerica. It must have been a (i)_____ process: cacao trees do not easily sprout from seed, need years to mature, and grow only in humid lowland forest. Moreover, in a tropical climate, cacao pods spoil quickly, rendering their transport from lowland Amazonia tropical Mesoamerica in a single journey by foot or canoe (ii)_____.
答案：B,D