The correct answer is option C, that is, bacteria.
Lightning produces a comparatively minute concentration of ammonia. However, the foremost transformation of nitrogen to ammonia is done by the microorganisms in the process known as nitrogen fixation.
All the nitrogen-fixing species are bacteria. Some of them live unconventionally from other organisms, thus also known as free-living nitrogen-fixing bacteria. Others live in close symbiotic relationships with plants or other species. The examples of nitrogen-fixing bacteria are Azotobacter and Cyanobacteria.
Answer: The parent plants both have heterozygous (YG) genotypes, there will be 25% YY, 50% YG, and 25% GG offspring on average. These percentages are determined based on the fact that each of the 4 offspring boxes in a Punnett square is 25% (1 out of 4).