Final answer:
Option 4.
Opposition is not a possible configuration for an inferior planet such as Mercury and Venus since they orbit inside Earth's orbit and thus cannot be positioned opposite the Sun from Earth's perspective.
Step-by-step explanation:
The configuration that is not possible for an inferior planet is opposition. Inferior planets, Mercury and Venus, orbit closer to the Sun than Earth does, and thus they never appear opposite the Sun in our sky, which is the requirement for an opposition.
The opposition occurs when Earth is directly between the Sun and a planet, which can only happen for superior planets (those orbiting beyond Earth's orbit such as Mars, Jupiter, and Saturn).
Inferior conjunction happens when an inferior planet passes between Earth and the Sun. Superior conjunction takes place when an inferior planet is on the opposite side of the Sun from Earth.
Greatest eastern elongation is when the planet is visible in the evening sky, well after sunset.