challenge: What is the outcome of the Lewy example in relation to the ∂¯b-complex?
  
  A. The ∂¯b-complex is almost never exact
  B. The ∂¯b-complex is always exact
  C. The ∂¯b-complex is exact for CR manifolds
  D. The ∂¯b-complex is sometimes exact
  Answer: 