Which Spanish city did Cornelia's husband establish good relations with, that Tiberius Gracchus was later sent to help attack?

The correct answer is based on historical events concerning the political and military relationships during the Roman Republic period. Cornelia, known as the mother of the Gracchi brothers, had connections to significant political figures and events of her time. Her husband, Tiberius Gracchus, is noted for his efforts in gaining allies during conflicts with various groups.

Numantia was a significant Celtiberian city known for its resistance against Roman forces. It is historically important because Tiberius Gracchus was sent in 134 BC to assist in the Roman campaign against it. The context of Numantia's resistance represents a crucial episode in the Roman expansion into the Iberian Peninsula.

The other cities listed—Carthago, Tarraco, and Saguntum—have their own historical contexts but do not fit the specifics of Tiberius Gracchus's military engagements in the same way that Numantia does. Carthago (Carthage) was a rival of Rome, mainly involved in the Punic Wars. Tarraco served as a major Roman outpost in Hispania and later became a prominent Roman provincial capital. Saguntum is known for its siege by Hannibal, preceding the Second Punic War, but does not relate