a – iv

b – iii

c – i

d – ii

Lactobacillus is a bacteria which converts the lactose sugar present in milk to lactic acid. Thus it helps in converting milk into curd.

Aspergillus is fungi which cause black mold disease on certain fruits and vegetables.

Spirogyra is an algae and is an important source of protein and are used as food supplements.

Paramecium is protozoa and is a minute, unicellular microorganisms found in water bodies.