Low air pressure systems are usually associated with a. clear, dry weather b. cloudy, wet weather c. cold, dry weather d. hot, dry weather

Low air pressure is related with high humidity. This is due to molecules of water (H2O) replace molecules of nitrogen (N2) and molecules of oxygen (O2). Water molecules are lighter than nitrogen and oxygen molecules (molar mass of H2O is 18 g/mol, molar mass of O2 is 32 g/mol, and molar mass of N2 is 28). Then lower mass means lower weight which translates into lower pressure (remember air pressure is the weight of the air per unit of area). Then, the answer is the option B. cloudy, wet weather.

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

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