Which of the following best fits the definition of a carrier in pesticide applications?

The choice referring to a substance that dilutes and suspends a herbicide aligns with the definition of a carrier in pesticide applications. In this context, a carrier is a material that helps distribute the active ingredient of a pesticide evenly and facilitates its application. By diluting and suspending the herbicide, the carrier allows for a more uniform application, ensuring that the herbicide reaches the target weeds effectively and reduces the risk of damage to non-target plants. Carriers can also help with the ease of handling and distributing the pesticide mix.

The other options do not fit the definition of a carrier as directly. A substance that enhances pesticide absorption relates more to adjuvants rather than carriers, as this focuses on how the pesticide interacts with the plant surface rather than on the physical transport and distribution mechanisms. A natural plant extract does not inherently serve the purpose of carrier in the context of pesticide formulations, and a method of application simply refers to how the pesticide is applied rather than what material acts as the carrier in the mix.