Final answer:
During Andrew Jackson's presidency, all white males were made eligible to vote for the first time, which was a significant political reform.
Step-by-step explanation:
During Andrew Jackson's presidency, which took place in the 1820s and 1830s, several political reforms occurred.
A. All white males were made eligible to vote for the first time. By the late 1820s, almost all adult white men had gained the right to vote. This expansion of democracy to nearly all white men was a significant political reform.
C. More presidential electors were being chosen by state legislators. This was not a political reform that occurred during Jackson's presidency, but rather a change that took place with the Twelfth Amendment in 1804.
D. Political parties started choosing presidential candidates by secret party caucus. While the caucus system had been used by political parties to select presidential candidates in the past, it was not a political reform that occurred during Jackson's presidency. The caucus system was eventually replaced by nominating conventions.