Emma is conducting a research project on texas during the 1840s and 1850s. which keyword search should she use to find information about why slavery grew

The slave population in Texas grew in the 1840s and 1850s because of the vast cotton plantations which needed a great many laborers. The settlers intended to create a cotton empire in Texas.  

Question: Which keyword search should she use to find information about why slavery grew

history of slavery in Texas/ cotton economy

the governor can not veto a referendum that the voters approve