Researchers studying the effects of toxic wastes knew that animals were poisoned by the heavy metal cadmium, but they wanted to know where cadmium accumulated in the body. the could find out by
a. finding out whether cadmium is acidic in water
b. tracing the movement of cadmium isotopes in test animals
c. measuring the size of cadmium atoms
d. finding out whether cadmium atoms form ionic or covalent bonds

b) tracing the movement of cadmium isotopes in test animals

Explanation: Cadmium is a type of soft metal that is found to be accumulating in the animal body. The appropriate way for finding the place of accumulation is by tracking the cadmium isotope's path in the body of test animal.

By tracing the movement of cadmium , the location where it stops and gets deposited can be reached and then best possible solution can be extracted to resolve the issue by researchers.

Other options are incorrect because finding acidity in water and size of cadmium is not relevant solution. The bond between the cadmium atoms also don't provide any relevance with the given situation.Thus, the correct option is option(b).

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

if you know your abc's you should be able to get your answer or just use google