1. **Problem:** Simplify the expression $6000 \div 1.5 \div 0.25$. 2. **Formula and rules:** Division is performed from left to right. So, first divide $6000$ by $1.5$, then divide the result by $0.25$. 3. **Step 1:** Calculate $6000 \div 1.5$. $$6000 \div 1.5 = 4000$$ 4. **Step 2:** Now divide $4000$ by $0.25$. $$4000 \div 0.25 = 4000 \times 4 = 16000$$ 5. **Answer:** The simplified value is $16000$. Therefore, the correct choice is **A. 16000**.