The answer is b damaged tissue can not be repaired
Answer : The value of rate constant is, 
Explanation :
First we have to calculate the rate constant, we use the formula :
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = ?
t = time passed by the sample = 20 min
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process = 100 - 85 = 15 g
Now put all the given values in above equation, we get


Therefore, the value of rate constant is, 
No it’s a decomposition reaction
Explanation:
Hint- look where the arrow is
If there is 1 product with an arrow next to it, then it is a decomposition reaction
This shows a product decomposing (breaking down) into 2 elements, which is a decomposition reaction