1.  harmful to man

2.  useful to man

4.  found only near banks of river

2.  Synthesis of proteins

3.  Synthesis of fat

4.  Synthesis of organic acids

1.  Zinc

3.  Boron

4.  Manganese

1.  coagulation of blood

2.  excretion

4.  digestion of blood

1.  Iron

2.  Sulphur

3.  Potassium

1.  Insects

3.  Snail

4.  Jelly fish.

1.  Jointed appendages

3.  Perriodic moulting

4.  Articulated exoskeleton.

2.  Light

3.  Temperature

4.  Availability of carbon dioxide

2.  Mn

3.  Zn

4.  Cu

1.  Insects

2.  Crab

3.  Shrimps