If `overset(vec)(F)` is force vector, `overset(vec)(v)` is velocity , `overset(vec)(a)` is acceleration vector and `overset(vec)(r)` vector is displacement vector `w.r.t.` mean position than which of the following quantities are always non-negative in a simple harmonic motion along a straight line ?
A. `overset(vec)(F).overset(vec)(a)`
B. `overset(vec)(v).overset(vec)(r)`
C. `overset(vec)(a).overset(vec)(r)`
D. `overset(vec)(F).overset(vec)(r)`