| A.Old Trees Communicate Like Humans |
| B.Young Trees Are In Need Of Protection |
| C.Trees Contribute To Our Society |
| D.Trees Are More Complex Than You Think |
| A.compete for survival | B.protect their own wealth |
| C.depend on each other | D.provide support for dying trees |
| A.“mother trees” are usually of no use to other trees. |
| B.Charles Darwin had the same thought as Simard. |
| C.if “mother trees” are cut down, the survival for the entire forest will be affected. |
| D.people know much about the complex “tree societies”. |
| A.how “tree societies” work |
| B.how trees grow old |
| C.how forestry industry develops |
| D.how young trees survive |