Question

E-shopping, when properly _____ ,can save us a lot of time and energy

1. A.
   done
2. B.
   doing
3. C.
   to do
4. D.
   is done

Answer 1

A
考查非谓语动词。逻辑主语E-shopping与do之间的关系为被动关系，故用过去分词，相当于when it is done properly，选A。