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What is the BEST interpretation of the integral: $F(x)=\int _{ a }^{ x }{ f(t)dt } $?

The antiderivative of $f(x)$.

The accumulated area under the curve of $f(x)$ from an initial point $a$ to a variable $x$.

The actual area under the curve of $f(x)$ from $a$ to $x$.

The initial value of $F(t)$.