The longest bone in the human body is
Ulna
Humerus
Femur
Tibia
C.
Femur
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