Final answer:
Child labor has been largely eradicated in the U.S. due to strict labor laws, compulsory education, and mechanization of jobs. However, it persists in parts of the world where economic necessity and weak enforcement of laws allow it to continue. The correct option is A.
Step-by-step explanation:
Child labor no longer exists in the U.S. today primarily due to strict labor laws and regulations that have been implemented over the years to protect the welfare of children. The development of compulsory education laws and the progressive reforms of the early 20th century also shifted children from workplaces to schoolrooms.
Factors such as greater mechanization of factories, which eliminated many jobs suitable for children, and a series of legislative efforts, including those by local anti-child labor organizations, led to the dramatic decrease in child labor in the U.S. by the beginning of the twentieth century.
In contrast, child labor still exists in other parts of the world due to a combination of economic factors and lack of enforcement of labor laws. In many low-income countries, families depend on the income generated by their children to survive, and the enforcement of existing labor laws may be lax due to limited resources or corruption. Thus, despite the existence of laws against child labor in various countries, practical enforcement and economic necessity often lead to continued child employment.