1. What is monotonic reasoning? What is nonmonotonic reasoning? 2. How is default rules represented in default theory? What representation forms does there exist? 3. A default theory is a pair T=, with Da set of default rules and W a set of closed formulas. Please represent the following sentences with such a default theory. Some mollusks have shell (2) Cephalopods are mollusks. (3) Not all cephalopods have shell. 4. Both the closed world assumption and the circumscription are formalisms for nonmonotonic reasoning. Please exposit these two formalisms and compare the difference between them. 5. Represent the following situations with the truth maintenance system: (1) It is now summer. (2) The weather is very humid. (3) The weather is very dry. 6. How to maintain the consistence of a knowledge base by the truth maintenance system? Please illustrate it with an example. 7. Please represent the following monkey-and-bananas problem with situation calculus. The world is composed of a monkey in a room, a bunch of bananas hanging from the ceiling, and a box that can be moved by the monkey. The bananas are out of the reach of the monkey; however, the box will enable the monkey to reach the bananas if the monkey climbs on it. The actions available to the monkey include Go from one place to another, Push an object from one place to another, ClimbUp onto or ClimbDown from an object, and Grasp or Ungrasp an object. Initially, the monkey is at A, the bananas at B. and the box at C. The question is how to get the bananas. 8. What are the basic elements of the description logic? 9. How are actions represented in the dynamic description logic