Which organism is highly useful for soil fertility?

Which of the following is a biofertilizer reported to increase rice production by more than $50\%$?

The common nitrogen fixer found in paddy fields is . . . . . . .

Consider the following four statements $(A - D)$ related to organic farming and select the correct option stating which ones are true $(T)$ and which ones are false $(F)$. The statements :
$(A)$ Produces food crops rich in lipids,vitamins and iron
$(B)$ Uses biofertilisers which increases soil fertility
$(C)$ There is more use of chemical fertilisers and pesticides
$(D)$ Raising unpolluted crops through the use of bacteria,fungi and cyanobacteria

The biofertilizer present in the roots of legumes is

Which of the following is used as biofertiliser?
$I.$ Cyanobacteria
$II.$ Yeast
$III.$ Symbiotic bacteria
$IV.$ Free living bacteria
Choose the correct option.