The given system is a first-order system with a transfer function of 2/s, where 's' represents the Laplace variable. To find the time taken for the step response to reach 98% of its final value, we can analyze the system's response using the time-domain approach.

Step Response Analysis:
The step response of a system is the output when a unit step input is applied to the system. In the Laplace domain, a unit step function is represented as 1/s.

1. Find the Transfer Function:
The transfer function of the given system is 2/s.

2. Determine the Step Response:
To find the step response, we need to multiply the transfer function by the Laplace transform of the unit step function (1/s).

Step response = 2/s * 1/s = 2/s^2

3. Find the Time-Domain Equation:
To convert the Laplace domain equation into the time domain, we can use the inverse Laplace transform. In this case, the inverse Laplace transform of 2/s^2 is a delayed unit step function.

Time-domain equation = 2 * (t - t0)

where 't0' represents the time delay.

4. Determine the Time taken to reach 98% of the Final Value:
To find the time taken for the step response to reach 98% of its final value, we need to determine the value of 't' when the step response equation reaches 0.98 times its final value.

0.98 * (t - t0) = 2 * (t - t0)

Solving the equation, we get:

0.98t - 0.98t0 = 2t - 2t0

0.02t = 0.02t0

t = t0

Since the equation simplifies to t = t0, we can conclude that the time taken for the step response to reach 98% of its final value is equal to the time delay, which is given as 4s in option C.

Therefore, the correct answer is option C (4s).