Which of the following is a synthetic auxin herbicide?

Synthetic auxin herbicides are a class of herbicides that mimic the natural plant hormone auxin, which regulates growth processes in plants. These synthetic variants disrupt normal plant growth and development, leading to uncontrolled growth and eventual plant death in susceptible species.

Each of the herbicides mentioned plays a role in this group. Clopyralid is effective against broadleaf weeds and certain woody plants, often used in turf and rangeland management. Quinclorac is noted for its use in controlling sedges and broadleaf weeds in various crops, exhibiting auxin-like activity that modifies growth patterns in target plants. Triclopyr is particularly known for its effectiveness against woody plants and invasive species, utilizing its synthetic auxin properties to influence growth in these plants.

The inclusion of all three options as examples of synthetic auxin herbicides shows the diversity of application and effectiveness of this type of chemical in managing various weed and plant issues. Hence, stating that all of the listed herbicides are synthetic auxins accurately captures the essential characteristics of these chemicals and their roles in pest management.