The *blank* of the line on a velocity vs. time graph represents acceleration

the slope of the line on a velocity vs. time graph represents acceleration

Explanation:

Acceleration is equal to the ratio between the change in velocity of an object and the time taken:

On a velocity-time graph, this ratio corresponds to the slope of the line. In fact, corresponds to the increment in the y-value (the velocity), while corresponds to the increment in the x-value (the time), therefore their ratio corresponds to the definition of slope of the line.

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

c.the charges if the proton and electron and gravity