Why do we put salt on the floor in the winter?

Can someone me with questions 15 to 17 plz.

What type of electromagnetic radiation has a shorter wavelength than blue light

Which of these is an example of pseudoscience? a) predicting the time of sunrise based on data on position of earth b) predicting the date of the moon phases based on data on position of earth c) predicting eclipses based on the position of the sun and the moon d) predicting future events in a person's life based on the position of the moon