Saltation velocity for dilute phase pneumatic transport of solids through a horizontal pipeline is

Question $5$Select one:

a$.$

The superficial gas velocity at which transported solids no longer completely remain suspended

b$.$

The superficial solids$/$particle velocity at which transported solids no longer completely remain suspended

c$.$

The actual gas velocity at which transported solids no longer completely remain suspended

d$.$

The relative velocity between the solid$/$particle and gas at which transported solids no longer completely remain suspended