The correct option is
A The oscillations in which the amplitude decreases gradually with the passage of time are called damped oscillations.
Equation of a damped oscillation is given by
y=A0e−γtsin(ω′t+ϕ)
This equation will be satisfied by the graph in option (a).
Graph in option (b) represents motion of a particle with variations in amplitude, but the amplitude of oscillations doesn't continuously decrease with time. So, option (b) is a wrong answer.
Graph in option (c) represents a particle whose amplitude increases with time and becomes constant at steady state. So, option (c) is also wrong.
Graph in option (d) represents a particle whose amplitude decreases with time exponentially but has no oscillatory motion. Hence, option (d) is also wrong.
Thus, option (a) is the correct answer.