Which of the following is the smallest bird?
Pigeon
Parrot
Humming bird
House sparrow
C.
Humming bird
The red, orange and yellow colours of leaves are due to
lignins
carotenoids
aldehydes
tannins
The optimum dissolved oxygen level (in mg/litre) required for survival of aquatic organisms is
4-6
2-4
8-10
12-16
The disease that kills more people than lung cancer as a consequence of air pollution is
heart attack
chronic bronchitis
asthma
emphesema