Vacuum boosters consist of all of the following components EXCEPT __ a. An outer housing b. One or two sealed diaphragms c. A combination valve d. A diaphragm return spring

## Step 1<br />Vacuum boosters are a type of brake booster that uses engine vacuum to amplify the force applied by the driver to the brake pedal. This amplification of force allows for easier and more effective braking.<br /><br />## Step 2<br />The vacuum booster consists of several key components, including an outer housing, one or two sealed diaphragms, and a diaphragm return spring. These components work together to create a vacuum that amplifies the force applied by the driver to the brake pedal.<br /><br />## Step 3<br />However, a combination valve is not a component of a vacuum booster. A combination valve is typically found in hydraulic braking systems, where it combines the functions of several valves into one. This is not a function of a vacuum booster, which operates using engine vacuum rather than hydraulic pressure.