As a result of the particles in a gas being in constant motion, gas has a . variable volume
variable Pressure
variable Shape
variable mass

i think it's variable pressure

if not soo advance sorry :)

a) the particles of the chair are strongly held together.

< > according to newton's third law of motion, forces always act in equal but opposite pairs. another way of saying this is for every action, there is an equal but opposite reaction.< >