ANS:B - Toothpaste pouring out of the tube.

The process that most closely resembles extrusion among the options provided is: "Toothpaste pouring out of the tube." Extrusion is a manufacturing process where a material, typically a metal or a polymer, is forced through a die to produce a continuous profile with a constant cross-section. In the case of toothpaste pouring out of the tube, a similar mechanism occurs where the toothpaste is forced out of the tube through a small opening, resulting in a continuous flow of toothpaste with a consistent shape and size. Let's briefly compare the other options to understand why they are not as similar to the extrusion process:

1. "Pneumatic ejection of abrasive solid particles through a nozzle": This process involves propelling solid particles through a nozzle using pneumatic pressure. While it involves the ejection of material through a nozzle, it doesn't involve shaping the material into a continuous profile with a constant cross-section, which is a key characteristic of extrusion.
2. "Ejection of abrasive slurry through an opening": Similar to the previous option, this process involves ejecting a slurry mixture through an opening. While it may involve shaping the material to some extent, it doesn't typically produce a continuous profile with a constant cross-section like the extrusion process.
3. "Viscous lubricant pouring out through its container's mouth": This process involves the pouring of a viscous lubricant from its container. While it involves the flow of material, it doesn't involve shaping the material into a continuous profile with a constant cross-section like extrusion.