Read the passage below and choose one correct answer for each question.

Over the past 600 years, English has grown from a language of few speakers to become the dominant language of international communication. English as we know it today emerged around 1350, after having incorporated many elements of French that we were introduced following the Norman invasion of 1066.

Until the 1600s, English was, for the most part, spoken only in England and hadn't extended even, as far as Wales, Scotland or Ireland. However, during the course of the next two centuries, English began to spread around the globe as a result of small enclaves of English speakers became established and grew in various parts of the world. As these communities proliferated, English gradually became the primary language of international business, banking and diplomacy. Today there are more than 700 million English users in the world, and over half of these are non-native speakers, constituting the largest number of non-native users than any other language in the world.

The world “proliferated” in paragraph 2 is closest in meaning to which of the following?