The body is protected against harmful flu viruses by

The immune system:

It is the part of the body that fights back disease

Explanation:

F=ma

since gravity is the only force acting on it

F=mg where F is the force exerted on the body, m is the mass, and g is the gravity with units m/s^2

given that the mass is 12.5kg and the force is 20N

20=12.5g

divide both sides by 12.5

1.6=g

the gravity is 1.6