Historical documents revealed American children worked in large numbers in mines, glass factories, textiles, agriculture, canneries, home industries, and as newsboys, messengers, bootblacks, and peddlers.And by 1900, their efforts had resulted in state and local legislation designed to prevent extreme child labor.
The best way to measure public opinion is through opinion polls - B
With opinion polls you get an idea what is the general idea about a certain topic from the public, as you usually get a high enough sample to deduce the relevant information.
To answer your second question I would say it is either B or C as being a sole proprietor usually makes you subjec to being a small business or you're forced to use factors of production less efficiently.
True the US joined in 1945 after the bombing of pearl harbour
<span>Progressive Era reformers at the turn of the century successfully compelled local governments to introduce 'civil service systems' to replace political machine.</span>
When he saw people falling, it made him think about the forces of nature and it lead him to his studies.
