IV Complete each sentence by writing the word in parentheses in the correct tense - either simple past or present perfect. (5 points) 1 Elon Musk, who ________________ (start) his first company when he was in his 20s, thinks he can solve some of the traffic problems affecting cities. 2 According to Richard Wurman, London ________________ (be) the largest city in the world in 1900. 3 Beijing ________________ (be) both the largest and most important city in China for hundreds of years. 4 Increased urbanization ________________ (cause) a number of problems for people living in them, including heavy traffic, rising crime, and loss of privacy. 5 Many scholars argue that the spread of agriculture about 10,000 years ago ________________ (allow) humans to begin living in towns and cities.