Answer:

Explanation:
= Velocity of one lump = 
= Velocity of the other lump = 
m = Mass of each lump = 
The collision is perfectly inelastic as the lumps stick to each other so we have the relation

The velocity of the stuck-together lump just after the collision is
.
The line at the bottom of the picture ... probably the first line on a list of choices .. is the correct equation.
Because the atoms and molecules all have different properties
It's not in motion when the line straight and flat . there's #9