Final answer:
Historically, cash crops such as tobacco and cotton required extensive manual labor, often provided by enslaved people, rather than mechanical harvesters, pesticides, or genetic modification.
Step-by-step explanation:
Crash crops such as tobacco and cotton primarily required manual labor during the time period associated with their extensive cultivation, particularly in the context of the Americas. These crops were labor-intensive, with processes like planting tobacco seeds by hand, transplanting seedlings, stripping leaves at harvest, and dealing with the cotton boll. While mechanical harvesters, pesticides, and genetic modification play significant roles in modern agriculture, during the historical periods when cash crops like tobacco and cotton were becoming established, manual labor was the critical component, often involving the exploitation of enslaved peoples.