Which NLP breakthrough significantly improved retail chatbots' ability to understand linguistic nuance in customer queries around 2018-2019?

Retail chatbots have transformed how customers interact with brands, especially in the language and linguistics industry. These AI assistants use natural language processing to understand customer queries, provide product recommendations, and even process transactions. But how well do you know the technological and linguistic innovations behind these virtual shopping assistants? Test your knowledge about the intersection of computational linguistics and retail technology!

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

BERT (Bidirectional Encoder Representations from Transformers)
Word2Vec embeddings
RNN (Recurrent Neural Networks)
LSTM (Long Short-Term Memory) networks