$5.$ In a slug flow, what is the slug?

A$)$ A mixture of gas and liquid moving at the speed of the liquid phase

B$)$ A large bubble that occupies the cross$-$section of the pipe

C$)$ Solid particles carried by the liquid phase

D$)$ A turbulent wave in the liquid phase

$6.$ How is the drift velocity defined in the drift flux model?

A$)$ The velocity of gas phase relative to the solid phase

B$)$ The velocity of the dispersed phase relative to the continuous phase

C$)$ The velocity of liquid phase relative to the gas phase

D$)$ The average velocity of all phases

$7.$ What is the main application of the three$-$phase flow theory?

A$)$ Single$-$phase flow in compact heat exchangers

B$)$ Multiphase flow in microgravity environments

C$)$ Gas$-$liquid$-$solid flows in chemical reactors

D$)$ Single$-$phase flow in large rivers

$8.$ Which equipment is NOT typically analyzed using gas$-$solid liquid dynamics?

A$)$ Bubble column reactors

B$)$ Trickle bed reactors

C$)$ Centrifugal pumps

D$)$ Fluidized bed reactors