The gravitational force of attraction on an object placed at the surface of the earth is known a weight of the object. The weight of the object is different on different planets because it depends on the gravitational constant.
The weight is defined by the Newton's second law as the product between the mass and the gravitational acceleration, that is
W = mg
And its unit in SI is Newton (N) and Lbf in American Unit.
Therefore the option D is the only correct here. 1600 kilo Newton or 1600kN.
Once the virus gets into the host's body, it enters the nearest cell.Once it gets to the nucleus it turns that cell into a virus-production cell and once the immune system detects those viruses it takes action.
I believe the answer to that question is A. If you can obtain the time it takes to reach the bottom of the cliff, then you can solve for the other two values.