Answer:
Embryonic stem cells could be used to make more specialized tissues that have been lost to disease and injury. For tissues that are constantly replaced, like blood and skin, stem cells would probably be replaced directly.
Explanation:
Answer: 100 grams of the parent isotope will remain after one half life.
Explanation:
Mass of the isotope present at initial stage = 
The mass of the parent isotope left after the time ,t=N
Time taken by the samle ,t = 
The half life of the sample :


![\ln[N]=ln[N^o]-\frac{0.693}{t_{\frac{1}{2}}}\times t_{\frac{1}{2}}](https://tex.z-dn.net/?f=%5Cln%5BN%5D%3Dln%5BN%5Eo%5D-%5Cfrac%7B0.693%7D%7Bt_%7B%5Cfrac%7B1%7D%7B2%7D%7D%7D%5Ctimes%20t_%7B%5Cfrac%7B1%7D%7B2%7D%7D)
![2=\frac{[N_o]}{[N]}](https://tex.z-dn.net/?f=2%3D%5Cfrac%7B%5BN_o%5D%7D%7B%5BN%5D%7D)
![[N]=\frac{N_o}{2}=\frac{200 g}{2}=100 g](https://tex.z-dn.net/?f=%5BN%5D%3D%5Cfrac%7BN_o%7D%7B2%7D%3D%5Cfrac%7B200%20g%7D%7B2%7D%3D100%20g)
100 grams of the parent isotope will remain after one half life.
In my opinion it is tears.