The correct answer is B. infinity.
The reflection coefficient is a dimensionless quantity that is used to describe the ratio of the reflected wave to the incident wave at a discontinuity in a transmission line. The reflection coefficient is given by the following equation:
$$\Gamma = \frac{Z_r – Z_0}{Z_r + Z_0}$$
where $Z_r$ is the characteristic impedance of the transmission line and $Z_0$ is the characteristic impedance of the load.
In the case of an open circuited end of a transmission line, the characteristic impedance of the load is infinite. Therefore, the reflection coefficient is given by:
$$\Gamma = \frac{\infty – Z_0}{\infty + Z_0} = -1$$
This means that the reflected wave is equal in magnitude to the incident wave but opposite in phase. This results in a standing wave pattern on the transmission line.
The other options are incorrect. Option A is incorrect because the reflection coefficient is not zero at an open circuited end of a transmission line. Option C is incorrect because the reflection coefficient is not unity at an open circuited end of a transmission line. Option D is incorrect because there is a correct answer to the question.