Which of the following quantities are always positive in a S H M

$\begin{array}{l}\overrightarrow{\mathrm{F}}\cdot \overline{\mathrm{a}}=\mathrm{m}(\overline{\mathrm{a}}\cdot \overrightarrow{\mathrm{a}})={\mathrm{ma}}^2\Rightarrow {\mathrm{a}}^2=\text{ always+ve }\\ \mathrm{m}=\mathrm{a}\text{lways +ve, so }\overrightarrow{\mathrm{F}}\cdot \overline{\mathrm{a}}\text{ is }+\text{ ve }\end{array}$

Force or acceleration and displacement are  always in opposite direction hence so F.r or a.r are always negative

V and r sometimes in the same direction sometimes in opposite direction so it could be +ve or -ve.