Which of the following were methods used by labor unions to secure better working conditions?

collective bargaining
piecework
strikes

strikes

Explanation:

The labor movement in the United States grew out of the need to protect the common interest of workers.  

To get their demands, the unions rely on various strategies, like strikes:

Workers refuse to return to work until their demands are fulfilled. The company comes to a standstill and consent to granting the union's demands.

apartheid, (afrikaans: “apartness”) policy that governed relations between south africa's white minority and nonwhite majority and sanctioned racial segregation and political and economic discrimination against nonwhites. people should not get this wrong. i was just answering a question.

world war i began in 1914, after the assassination of archduke franz ferdinand, and lasted until 1918. during the conflict, germany, austria-hungary, bulgaria and the ottoman empire (the central powers) fought against great britain, france, russia, italy, romania, japan and the united states (the allied powers). to new military technologies and the horrors of trench warfare, world war i saw unprecedented levels of carnage and destruction. by the time the war was over and the allied powers claimed victory, more than 16 million people—soldiers and civilians alike—were dead.

explanation: