The use of what was particularly important for the advancement of civil rights

The answer is the mobilization masses of people. This refers to deployment of civilian population as part of contentious politics. Mass mobilization is frequently used by grassroots-based social movements, including revolutionary movements, but can also turn into a tool of elites and the state itself. The procedure usually takes the form of large public gatherings such as mass meetings, marches, processions, parades,  and demonstrations. Those assemblies usually are part of a protest action.

The correct answer to this open question is the following.

Although there is no further context or references, we can comment on the following.

Congress can't raise a sitting president's salary because he is in function. Once the President's administration had ended, Congress can consider a raise to the President's salary, but not until the term is done.

The concern of Congress is that the President could get the money that can be used for other necessities and priorities of the federal government. Let's have in mind that there is an office in Congress that oversees and confirm the budget prepared by the office of the President. No other concept can be included if was not authorized by Congress.

The President cannot decide when to raise his salary and for how much. Congress tries to avoid any corruption act in this regard.

This is an important control mechanism that resulted from the checks and balances system established by the United States founding fathers when they created the US Cönstitution during the Constitutional Convention of Philadelphia, Pennsylvania in 1787.

This checks and balances system prevents any federal branch to have more power than the other two, trying to keep a healthy balance of power in the federal government.

Today, the US President's salary is approximately $400,000 a year.