The word their” in the passage refers to .

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 39 to 45.

When General O. O. Howard assumed his duties as commissioner of the Freedmen's Bureau on May 12, 1865, he faced no problem more difficult than that of affording freedmen legal protection. Despite the fact that the war had dealt a death blow to slavery, the legal status that blacks would occupy as free men was uncertain when the war ended.
In the pre-war period, Southern state law has discriminated against free blacks, providing harsher criminal punishment for them than for whites, denying them the right to testify against whites, and severely restricting their liberty in numerous ways. In the war's aftermath, Southern whites, rapidly able to gain control of their state and local governments under President Andrew Johnson's program of reconstruction, stood ready to apply this discriminatory law to the freedmen. Nor was the problem of affording freedmen legal protection limited to shielding them from enforcement of discriminatory state law.
In the post-war period, Southern whites, fearful of the consequences of liberation, resorted to violence on a massive scale in order to maintain their dominance over blacks. And in the face of this violence, Southern state law enforcement and judicial officials generally proved to be either unwilling or unable to bring to justice whites who had committed acts of violence against freedmen. Moreover, the problem of protecting black workers against immoral employers also confronted Howard and his subordinates.
Although the Freedmen's Bureau Act authorized them to lease and ultimately to sell abandoned land to freedmen, Andrew Johnson's policy prevented Bureau officials from using that authority to make blacks landowners. Consequently, in order to support themselves, most freedmen found it necessary to work for whites as plantation and farm laborers. And given impoverished planters' inability to pay laborers in cash at the end of each month, most black laborers had little choice but to agree to work for planters for an entire year and to receive their pay, in either cash or a share of the crop, at the end of the year. In this situation, white employers, many of whom were eager to pay their workers as little as possible, had numerous opportunities to deny freedmen’s right.