$5.$ Liquid$-$liquid flow in pipelines is often characterized by:

A$)$ The formation of a gas cap

B$)$ The dispersion of one liquid phase into another

C$)$ Complete miscibility of the two phases

D$)$ The absence of interfacial tension

$6.$ Which of the following is a characteristic feature of bubbly flow?

A$)$ High pressure drop

B$)$ Presence of large, elongated bubbles

C$)$ Random distribution of small gas bubbles in the liquid phase

D$)$ Stratification of phases due to density differences

$7.$ In the context of three$-$phase flow, the term "holdup" refers to:

A$)$ The delay time in a packed bed reactor

B$)$ The volume fraction of one phase in the mixture

C$)$ The pressure drop across a fluidized bed

D$)$ The velocity difference between phases

$8.$ Which equipment is not typically used for gas$-$solid$-$liquid reactions?

A$)$ Bubble column

B$)$ Pneumatic conveying systems

C$)$ Trickle bed reactor

D$)$ Agitated vessels