21. The following are the advantages of the small shelters except ________.

   A. saving power and energy

   B. protecting possessions of the homeless

   C. decorating the streets where they are

   D. keeping the homeless safe and comfortable

22. We can learn from the passage that ________.

   A. Greg Kloehn has sold at least 20 tiny houses

   B. An act of kindness has made people simple and grateful

   C. The shelters are immovable

   D. The government has got involved in the action

23. The passage is likely taken from ________.

   A. An official report         B. An art review

   C. A science magazine       D. A news report