Chocolate, which must be one of the world's most __1__ foods, first came to ___2__ in the 16th century from __3___. The Aztecs used to crush the beans into a __4___ and add ___5__ to make a stimulating and nourishing drink. It was used in _____6__ ___7_____. Solid chocolate was first appeared in the __8___. The process of getting cocoa butte was first tried in ___9__. In _10_____, Rodolphe Lindt of Switzerland began to add extra cocoa butter to his chocolate, making it ___11___. ____12__ is the world's best-selling type of chocolate, which is sweeter and smoother than ___13___. If a parent likes chocolate, so does the __14___. The ___15___ trait makes us prefer to eat things with a sweet taste. The chocolate helps release __16___ in the brain called endorphins. The chemicals make us feel _17___ and give us a sense of __18___.