$\begin{array}{1 1} \text{a. When agricultural fields are sprayed with DDT, it is carried by run off water into nearby aquatic bodies.} \\ \text{b. River water may have very low concentration of DDT, but the carnivorous fish in that river may contain high concentration of DDT, which is still suitable for consumption by human beings.} \\ \text{c. Increased concentration of DDT in birds affect calcium metabolism due to which egg shells become thin and break before maturity.} \\ \text{d. None of these.} \end{array}$
