Final answer:
The Pantheon was rebuilt around 125 CE by Emperor Hadrian, making it the last structure to be built among the options given. The correct option is B.
Step-by-step explanation:
To determine which of the given structures was built last, we can review their construction dates. The Sanctuary of Fortuna Primigenia dates back to the 2nd century BCE, making it the oldest among the options. The Forum of Augustus was constructed as a part of the series of Imperial fora in ancient Rome.
The Pantheon as we know it today was rebuilt by Emperor Hadrian around 125 CE, suggesting that it is newer than the Sanctuary of Fortuna Primigenia and the Forum of Augustus.
We do not have a specific construction date for the House of the Tragic Poet, but it likely dates from the 2nd century BCE as well. Thus, among the listed options, the Pantheon is the structure that was built last. Option B. is the correct one.