Most cars today use an combustion engine a. internal b. external

A. internal

Explanation:

Engine is the name given to the equipment responsible for turning energy into motion of the vehicle in which it is installed. In the case of cars and other vehicles, the engine is called “internal combustion” because it transforms the burning of fuels in its interior in motion.

Regardless of engine type, everyone needs the same elements: air, fuel, and an explosion trigger. In Otto engines, this trigger is provided by the spark plug, which unleashes a spark inside the cylinder and generates the explosion. In diesel engines, such an explosion is generated by the compression of gases within the cylinder and the elevated temperature.

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

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.