What type of pesticide is most commonly used due to its broad effectiveness?

The most commonly used pesticide being non-selective is correct because non-selective herbicides are designed to kill a wide range of plants, including both weeds and desirable vegetation. This broad-spectrum effectiveness makes them particularly useful in various agricultural and landscaping applications where quick and efficient removal of unwanted plants is necessary.

Non-selective pesticides can be advantageous for controlling invasive species or in situations where extensive weed management is required, as they act on most plants that they come into contact with. Their ability to eliminate a variety of plant life quickly makes them a popular choice among those looking to manage overgrown areas or prepare land for planting.

In contrast, selective herbicides specifically target certain types of plants while leaving others unharmed. While these can be beneficial in preserving desired vegetation, they do not offer the same broad effectiveness as non-selective options. The same reasoning applies to contact pesticides, which only act on organisms they physically touch, and systemic pesticides, which are absorbed by plants and can affect specific pests but not necessarily a broad range of plants. Thus, non-selective pesticides remain the go-to choice for general and widespread use in controlling undesirable plant growth.