Answer:
In WWI, the tank was slow and unreliable, but effective.
Explanation:
As we know WW1 brought many changes when it comes to war efforts. New techniques were introduced and among them usage pf tanks.
Those tanks were heavy and slow, but still practically unbroachable. They were used for the first time in 1916, but until the end of the war were used more frequent.
The correct answers are working on a history test and solving a sudoku puzzle.
The reason for this is because you can listen to music and don't need to be explicitly conscious - imagine drifting away in thoughts while you listen to music, or do something completely unrelated.
The same goes for riding a bike. Once you know how to ride a bike and know the path where you're going, your attention and explicit consciousness can be allocated somewhere completely else :)
The correct answers are the middle two - because of them require you to be present and attentive of the situation and what you have to do.
D)they wanted to give freed slaves a path to equality