Select the incorrect from following?

Options

A. Both Rhizobium and Frankia can be free living in soil
B. Plants cannot use nitrate directly that is why nitrate
assimilation occurs in plants
C. Azotobacter and Sinorhizobium are able to fix `N_(2)` in free state
D. Nitrifying bacteria utilize energy released during nutrification

Answer

To solve the question, we need to evaluate each of the four statements provided regarding nitrogen fixation and identify the incorrect one.

### Step-by-Step Solution:

1. **Evaluate the First Statement:**
- **Statement:** "Both Rhizobium and Francia can be free living in soil."
- **Analysis:** This statement is correct. Rhizobium and Francia are nitrogen-fixing bacteria that can exist freely in the soil and do not necessarily need to form a symbiotic relationship with plants to fix nitrogen.

2. **Evaluate the Second Statement:**
- **Statement:** "Plants cannot utilize or cannot use nitrate directly, which is why nitrate assimilation occurs in plants."
- **Analysis:** This statement is also correct. Plants cannot directly use atmospheric nitrogen; they need it to be converted into forms like nitrate or ammonia through processes such as nitrate assimilation before they can absorb and utilize it.

3. **Evaluate the Third Statement:**
- **Statement:** "Azotobacter and cyanorhizobium are able to fix nitrogen in free state."
- **Analysis:** This statement is incorrect. Azotobacter is a free-living nitrogen-fixing bacterium, but cyanorhizobium (often referring to cyanobacteria that form symbiotic relationships) typically does not fix nitrogen in a free state. Therefore, this statement is misleading as it implies both can fix nitrogen freely.

4. **Evaluate the Fourth Statement:**
- **Statement:** "Nitrifying bacteria utilize energy released during nitrification."
- **Analysis:** This statement is correct. Nitrifying bacteria, which play a role in converting ammonia to nitrate, do indeed utilize the energy released during the nitrification process for their metabolic activities.

### Conclusion:
The incorrect statement is the third one: "Azotobacter and cyanorhizobium are able to fix nitrogen in free state."