Which of the following relationships between the acceleration a and the displacement x of a particle executing simple harmonic motion?

Which of the following relationships between the acceleration a and the displacement x of a particle involve simple harmonic motion?

Which of the following relationship between the acceleration a and the displacement x of a particle involve simple harmonic motion ?

Which of the following relationship between the acceleration a and the displacement x of a particle involve simple harmonic motion ?

Which of the followng relationships between the acceleration a and the displacement x of a particle involve simple harmonic motion? a= 0.7x .

Which of the followng relationships between the acceleration a and the displacement x of a particle involve simple harmonic motion? a= - 10x