A collection of nodes capable of environmental sensing, local computation, and communication with its peers or with other higher performance nodes

The correct answer is D. sensor network.

A sensor network is a collection of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc., and to cooperatively pass the data to a main location.

A voice portal is a computer system that can understand and respond to spoken commands.

A mobile portal is a website or application that is designed to be accessed on mobile devices, such as smartphones and tablets.

Geolocation is the process of determining the geographic location of an object, such as a person, vehicle, or device.