Answer/Explanation:
A theory has lots of scientific evidence to back it up. We know this to be true based on lots of different diseases and studies of their spread.
A hypothesis is more of a starting point - an educated guess based on limited evidence. It requires further testing before becoming a theory.
A law is something that can be generalized to lots of contexts, and is universal. Such as the law of thermodynamics.
The answer for this is 26.6°c
Answer:
The question you have provided is incomplete
Explanation:
Half-life is the time taken for the concentration of the substance to reduce by 50%. The original sample of strontium had a mass of 1.6 gms. Thus, option d is correct.
<h3>What is half-life?</h3>
The half-life of any radioactive substance is the time period at which the concentration will get reduced to half the initial amount. The initial mass of Sr-90 is calculated as,

Given,
Quantity of the remaining substance N (t) = 0.40 gm
Initial radioactive substance quantity
=?
Time duration (t) = 56 years
Half-life = 28 years
Substituting values above:

= 1.6 gm
Therefore, option d. the initial mass of Sr is 1.6 gm.
Learn more about half-life here:
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