Final answer:
The student's fill-in-the-blanks question is correctly completed with 'a) Folk customs; popular culture', describing the diffusion of traditional practices from the Old World to the New World, and the cultural blend in the Mid-Atlantic and Midwest forming a new mainstream culture.
Step-by-step explanation:
The term 'folk customs' refers to traditional practices developed by small, homogeneous groups living in isolated rural areas. These customs often reflect cultural heritage and can include techniques of house-building, traditional dress, or religious practices passed down over generations. The spread of folk customs into a different area is referred to as relocation diffusion. The initial settlers in the New World brought their Old World concepts and artifacts, influencing the native populations and their practices through this diffusion.
The term 'popular culture' describes a set of shared practices, attitudes, and values that are common in large, heterogeneous societies, heavily influenced by mass media and interchangeably following global trends. The sentence's second part describes the mix of various European immigrant influences that formed a unique pioneering culture in the Mid-Atlantic and Midwestern United States, a reflection of popular culture during the antebellum period.