This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
True about certain lethal dose (CLD): 
Select and explain. 
A. 2 times of safely tolerated dose, B. 4 times of safely tolerated dose, C. 5 times of safely tolerated dose, D. 6 times of safely tolerated dose
B: 4 times of safely tolerated dose
Answer: B: 4 times of safely tolerated dose 
Explanation: Fluoride toxicity:

Safety recommended dose — Above 3 yrs old child is 1mg/day and adult 1.7 - 3.3 = 2.2 approx.
STD (safety tolerated dose) — 8 to 16 mgF/kg wt.
CLD (certain lethal dose) — 32 to 64 mgF/kg wt (4 times of STD) = 56 g.
Probable lethal dose = 5 mg/kg wt.

Essentials of preventive and community dentistry 
Soben Peter 
5th edition