Explain the concept 'census'?

A group of librarians is interested in the numbers of books and other media that patrons check out from their library. They examine the checkout records of $150$ randomly selected adult patrons.

Identify the population and sample in this setting.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

A quality control engineer is curious about the thickness of paint on a car at her factory. She randomly selects $30$ points on the car and measures the paint thickness at each of those points.

Identify the population and sample in this setting.

The state Department of Transportation wants to know about out-of-state vehicles that pass over a toll bridge with several lanes. A camera installed over one lane of the bridge photographs the licence plate of every tenth vehicle that passes through that lane.

Then the population and sample in this setting is all the vehicles that pass over the toll bridge; the sample is vehicles from the lane with the camera.

Dakarai is comparing two books: $A$ and $B$. He predicts that book $A$ has longer words than book $B$. What are the two populations here?