Thunderstorms require lift to form. Which of these factors causes lift in the atmosphere?
radiation
conduction
water vapor
convection

Option D, Convection

Explanation:
The four main mechanisms that lift the air in the atmosphere and create clouds are a) Convection; b) Convergence; c) Updraft and d) Orographic Lifting
Radiation, conduction and water vapor are not responsible for creating lift in the atmosphere.  
In convection, heat energy from sun raises the temperature of surface of the earth as it passes through the atmosphere. The air near the surface become less dense  and hence starts rising thereby creating a lift.
Hence, option D is correct

Convection is the answer to the question

They must use the scientific method

There would be one bar shorter than the bar for peaches.