From the graph above, R represents A. marginal cost B. total cost C. variable cost D. fixed cost

Fixed cost ($D$) is constant regardless of output, so it is a horizontal line parallel to the output axis.
Variable cost ($C$) is zero at zero output and increases with output, passing through the origin $(0,0)$.
Total cost ($B$) is fixed cost plus variable cost, so it is upward-sloping like variable cost but shifted upward (does not pass through the origin).
Marginal cost ($A$) is the slope (derivative) of total cost, typically U-shaped.

Curve $R$ is upward-sloping and curved, starting above the origin (not passing through $(0,0)$) and rising as output increases.
It is not horizontal, so not fixed cost ($D$).
It does not pass through the origin, so not variable cost ($C$).
It is not the steepest slope (typical of marginal cost at low output), so not marginal cost ($A$).

Curve $R$ matches total cost: upward-sloping from above the origin.

Final answer: $R$ represents total cost.
B