Which of the following statements is not true of nitrogen-fixing bacteria? they provide an important way for biologically available nitrogen to enter ecosystems. they live in root nodules. they are very common in symbioses in all plant families. some are free-living in the soil. they are very common in symbioses with plants from the legume family.

The correct answer is They are very common in symbiosis in all plant families.

Explanation:

Nitrigen fixation is a process in which the atmospheric nitrogen is converted to ammonia by the help of nitrogen fixing bacteria such as azobacter, clostridium.

     These bacteria lives in the root nodules of leguminous plants and some of them are free living soil bacteria such as azobacter.

   These bacteria only form symbiotic relationship with the root leguminous plants but not with other plant families.

the correct answer is d