使用暗筒式日照计需要每天在日落后换纸，如果是全日阴雨，无日照记录时可以不换。
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How can Uber attract more customers according to Para.7?
A. By word of mouth
By professional drivers
C. By Uber Pool
D. By private car owners
How did Airbnb find the property owners willing to share their places?
A. By knocking on their doors one by one.
By taking inviting pictures of their homes.
C. By advertising on the social media.
D. By contacting them after knowing their information from Craigslist.
How did Uber acquire its first bunch of customers in Para 10?
A. It provided sufficient taxis in big cities.
B. It launched service when the demand is the highest.
C. It gave big crowds of people free service.
D. It won a competition against main taxi companies.
What is the main idea of para. 16?
A. Ways of advertising must change with the growth of a company.
B. A company should persist in one single way of marketing.
C. A company may go through different stages on the way to success.
Digital marketing is a better way to attract new customers.
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