If any grammar has more than 1 LMD or more than 1 RMD or more than 1 parse tree that will be an ambiuous grammar.SO if grammar is unabiguous it must have only 1 LMD or 1RMD or 1 parse tree.
So here every umbiguous grammar has only 1 LMD and 1 RMD means both must be equal because if it is not it will be ambiguous.
TRUE