Out of the followings, which cannot be negative?

A fly is in rectilinear motion as described by the graph. The average speed of the fly is

The velocity $\left(V\right)$-time $\left(t\right)$ graph for the linear motion of an object is shown in the figure. The displacement and distance after $8 \mathrm{s}$, respectively are

The position vector of a particle is given by $\overrightarrow{r}=\left(2\hat{i}+3\hat{j}+4\hat{k}\right)\mathrm{m}$. The magnitude of the position vector is