A scalar is a mathematical term for: a. measurement
b. Magnitude and Direction
c. A number and a unit
d. A Scale

c. A number and a unit

Explanation:

A scalar is a real number. We often use the term scalar in the context of vectors or matrices, to stress that a variable such as a is just a real number and not a vector or matrix.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.