People who oppose labor unions believe that unions
keep more qualified workers from being hired.
create more new jobs than workers can fill.
make many businesses more competitive.
encourage employers to reduce salaries.

A managed establishment of workers comprising traders, factories labourers are called a labour union.

It is formed to guard the privileges and claims of the labours. Labour union fights for more acceptable working situations and earnings.

The correct option is:

Option A. keep more qualified workers from being hired.

This can be explained as:

Therefore, people against unions believe that they keep more qualified from being hired.

To learn more about union labour follow the link:

link

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain

we need the map to answer the question