Hello! 
A half-life is the amount of time it takes half of an element to decay. For example, after one of carbon's half-life, half of carbon would've decayed.
Now, we can calculate how much has decayed if 5 half lives have passed.
1 -> 50% (1) -> 25% (2) -> 12.5% (3) -> 6.25% (4) -> 3.125% (5)
Therefore, there would be 3.125% left of iodine. However, your question is asking what percent has decayed. Therefore, subtract 3.125 from 100% to get your final answer.
100 - 3.125 = 96.875
Therefore, your final answer is 96.875% of iodine has decayed if 5 half lives have passed.
Hope this helps!
 
        
             
        
        
        
Because we have carbon in the ground in the air and every were else
        
             
        
        
        
Answer:
D
Explanation:
Units of weight and volume won't be large enough to be meaningful. so liters and grams are too small. Find out the weight of a cubic meter of water and then estimate how many cubic meters there might be in a lake. Millions would probably be too small.
Miles are too big. Most lakes do not go to a depth of 1 mile, but you on on the right track. Distance is what you want. 
Meters are the answer.
 
        
                    
             
        
        
        
Answer:
1. True
2. True
3. False, they have 46
4. False, they inherit traits from both parents
5. True
6. False, rice has 12 pairs of chromsomes and flies have 4 so not all orangisms have the same number of chromosomes
7. True (not too confident with this one though)
8. False, a body cell has 46 while gametes have 23
9. False
10. True
Explanation: