Final answer:
Brodifacoum is a rodenticide that can depress clotting for 3-4 weeks by inhibiting the recycling of vitamin K.
Step-by-step explanation:
The rodenticide that can depress clotting for 3-4 weeks is brodifacoum.
Brodifacoum is a coumarin-based anticoagulant that is commonly used as a rodenticide. It works by inhibiting the recycling of vitamin K, which is necessary for the production of clotting factors in the blood.
It should be noted that brodifacoum can pose a serious risk to non-target animals and should only be used with caution and according to label instructions.