Given a scientific passage and an answer, generate a question for the given answer.

Passage: Carbohydrates include sugars, starches, and fiber. Sugars and starches are used by the body for energy. One gram of sugar or starch provides 4 Calories of energy. Fiber doesn't provide energy, but it is needed for other uses. At age 13 years, you need about 130 grams of carbohydrates a day. Figure below shows good food sources of each type. Answer: 4
How many calories of energy does one gram of sugar or starch provide?

Passage: Hydraulic car lifts also use fluid to transmit pressure and increase force. The lifts are used to raise cars, which are very heavy, so mechanics can work on them from underneath. Controls in airplanes use fluids to transmit pressure and increase force so a flick of a switch can raise or lower heavy landing gear. To see animations of hydraulic systems such as these, go to URLs:. Answer: hydraulic systems
What kind of systems use fluid to transmit pressure and increase force?

Passage: Ionic substances dissociate into ions when they dissolve in water, but most molecular substances do not. Answer: ionic
What substances dissociate into ions when dissolved in water?