What kind of marketplaces focus on spot requirements of larger firms in a single industry?

The correct answer highlights the role of exchanges in facilitating transactions that center around the immediate needs or "spot requirements" of larger firms within a specific industry. Exchanges are online platforms where buyers and sellers can connect to trade goods and services in real time. They are particularly effective in industries where firms require quick access to products, allowing for immediate fulfillment of demand.

Exchanges operate in a manner that caters to the dynamic nature of market demands, making them suitable for larger firms that often need to respond rapidly to changing business conditions. These platforms create a centralized marketplace where various suppliers and buyers are matched, enhancing the efficiency and speed with which transactions can occur.

Other options refer to different types of online interactions or procurement processes. Extranets, for example, serve as private networks that enable secure data sharing among specific groups, which is not focused on immediate spot buying. E-purchasing pertains more to the process of acquiring goods and services electronically but doesn’t specifically address the marketplace dynamics. E-distributors are typically sellers that focus on distributing products, but may not necessarily concentrate on fulfilling the spot needs of large firms in a specific industry.

Thus, exchanges stand out as the correct option because they directly facilitate transactions that align with the immediate and specific needs of larger firms within