(a) Aarti has displayed awareness and care towards the health of her sister.
(b) During the intake of different elements and compounds, the biological organisms absorb them differently. Also, the exact distribution of the elements and their function in the various parts of organisms cannot be known clearly. For this, a radioisotope is made ot enter the organism along with the elements and compounds, whose absorption, functioning and distribution to the brain has to be studied. The radioisotope act as a tag of label for the elements or compound under study. BY detecting the radiation emitted by the isotope from the brain, the regarding the absorption and function of the compounds by the organisms, are found out. In this way, radioisotope help a doctor to diagnose brain tumour.