Q19. | A human sperm may contain? X-Chromosome Y-Chromosome XY-Chromosome |
Q21. | Identical twins arise when two. |
Q22. | As in the arms and legs, blood flows against gravity and is prevented from flowing back by. |
Q23. | About....... of the total calcium present in the human body is in the blood. |
Q24. | The heart is covered by a membrane called. |