What makes Twitters ads well-known？
Ads writers would like to promote their own work.
B. Professional ads writers have produced many creative ads.
C. Many companies provide support since they can benefit from the ads.
D. A lot of followers are willing to buy self-branding products.
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______the explosion occurred was that the laboratory attendant had been careless.
A. That
B. What
C. Why
D. How
What is said about Twitters business model？
A. There has been a complete set of business model since Twitter was established.
B. Twitter"s employees are encouraged to have brainstorms for better business model.
C. Twitter has worked out detailed business model about how to support itself.
D. With the passage of time. Twitter has managed to improve its business model.
It is essential that these application forms______back as earlier as possible.
A. must be sent
B. will be sent
C. are sent
D. be sent
All this leads to a population in the twenty-first century that is smaller______feared few
A. than was
B. that was
C. than that
D. it was
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