Aztecs built chinampas ('floating gardens') in order to provide additional farm lands (answer C). The idea was to grow crops in small rectangular areas (ci. 30 x 2.5 m) on shallow lake beds. Aztecs began to use chinampas in Tenochtitlan in about 1250 AD.
The Aztecs built chinampas primarily to provide additional farmlands, which were essential for feeding their growing population. This innovative agricultural technique emerged around 1250 AD in Lake Texcoco. Chinampas allowed for efficient farming and contributed significantly to the Aztec economy.
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