Answer:
1) Force of gravity or weight
2) Friction force
3) Magnetic force
A factory worker is carrying box of nails.
So in this situation of carrying box of nails the worker must applied a force to pull the box against the force of gravity on it. This force is equal to the weight of the nails.
Also for walking on the floor there must be force of friction between his shoes and the floor.
As the friction force becomes very small due to oil drop on floor his shoes slips on the floor and he fell down
Next he used a powerful magnet to collect the nails which falls on the floor so here he used magnetic force to pull all the nails.