revision sheet

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Across
  1. 4. drug given to increase the immunity of the body.
  2. 5. framework of the body.
  3. 6. attaches muscle to bone.
  4. 7. attaches bone to bone.
Down
  1. 1. animals with backbone.
  2. 2. obtained from the bark of the willow tree.
  3. 3. external hard covering.
  4. 4. small ring shaped bone.