Correct Answer  Option 2 : 1 m/s
2
CONCEPT:

Acceleration (a): The rate of change of velocity is known as acceleration.
\(\overrightarrow{a} = {\overrightarrow{Δ v} \over Δ t} \)
where a is the vector quantity, Δv is the velocity, and Δt is the time.
 To convert speed from km/h to m/s, we multiply it by 5/18.
CALCULATION:
Given:
V_{i} = 54 km/h = 54 × (5/18) = 15m/s and V_{f} = 72 km/h = 72 × (5/18) = 20 m/s and Δt = 5s
\(\overrightarrow{a} = {\overrightarrow{Δ v} \over Δ t} = {\overrightarrow{ v_f} \overrightarrow{ v_i} \over Δ t}\)
\(\overrightarrow{a} = {20 15 \over 5}=1m/s^2\)
 So the correct answer is option 2.