The first English-language Pokémon Trading Card Game set was called Base Set. Wizards of the Coast released it in the United States on January 9, 1999.
In Japan, the corresponding inaugural release was known as the First Starter & Expansion Pack and arrived in October 1996. The English name Base Set became the standard term used by players and collectors for the foundational English cards.
Jungle was the second English expansion, followed by Fossil. Team Rocket came later, so those names are plausible but incorrect answers to this question. The 1998 Pokémon Demo Game Plastic Pack can also cause confusion: it introduced sample cards in the United States, but it was not the first full English set.