_________ to explain it, she would not believe him．

1. A.
   However hard he tried
2. B.
   However hard did he try
3. C.
   How he tried hard
4. D.
   However did he try hard

To explain the cause of radiation is beyond the ________of my knowledge.

1. A.
   scope
2. B.
   content
3. C.
   application
4. D.
   understanding

To explain what they have seen, the scientists build a theory about the way ________ things happen and the causes and effects.

1. A.
   how
2. B.
   that
3. C.
   in that
4. D.
   which

To explain what they have seen, the scientists build a theory about the way ________ things happen and the causes and effects.

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