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Which one of the following options correctly describes the locations of the roots of the equation $s^{4}+s^{2}+1=0$ on the complex plane?

1. Four left half plane(LHP) roots
2. One right half plane(RHP) root,one LHP root and two roots on the imaginary axis
3. Two RHP roots and two LHP roots
4. All four roots are on the imaginary axis