It is difficult to smooth floor why

Complete question is:

It's is difficult to walk on a wet floor than a smooth floor. Why?

Because friction on wet floor is far lesser than on a smooth floor

Explanation:

On wet surfaces, the friction is far lesser than on smooth surfaces and thus the grip between the bottom of your shoes/feet and the ground is very very small and as such walking on the wet surface becomes more difficult. Whereas on Smooth surfaces, there is plenty of friction and as a result, there is enough grip between the bottom of your shoes/feet and the ground thereby making walking far easier.

real, smaller and upside-down.   so the answer should be b.

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.