The ribs moves upwards and outwards when we

More than half of total blood volume is the

A. red and blood cells

B. plasma

C. platelets

D. all of them

The special organ in mammals, birds and reptiles is

A. lungs

B. air sacs

C. stomata

D. spiracles

Platelets help in blood

A. producing

B. rejuvenating

C. clotting

D. purifying

The circulatory system of human is composed of

A. heart

B. blood

C. blood vessels

D. all of them

Ventricles are chambers of heart which are

A. upper

B. lower

C. middle

D. valves