$13.$ Pressure drop in multiphase flows is significantly influenced by:

A$)$ Pipe diameter alone

B$)$ Flow regime

C$)$ Temperature gradients

D$)$ Phase chemical composition

$14.$ Volume fraction estimation techniques are crucial for:

A$)$ Determining phase velocities

B$)$ Predicting flow regimes

C$)$ Designing equipment

D$)$ All of the above

$15.$ The drift velocity in the drift flux model represents:

A$)$ The velocity of gas relative to liquid

B$)$ The velocity of liquid relative to the pipe

C$)$ The average velocity of the mixture

D$)$ The velocity of one phase relative to the mixture's velocity

$16.$ In gas$-$liquid flows in mini channels, the modified drift flux model accounts for:

A$)$ Enhanced heat transfer

B$)$ Decreased interfacial tension

C$)$ Scale effects on flow patterns

D$)$ Increased gravitational forces