The aquatic fern used to increase the yield in paddy crops is Azolla. Azolla is a floating fern that can fix atmospheric nitrogen, providing a natural source of nitrogen to rice paddies.
So, the correct option is (A): Azolla
In a Vernier caliper, \(N+1\) divisions of vernier scale coincide with \(N\) divisions of main scale. If 1 MSD represents 0.1 mm, the vernier constant (in cm) is:
There are several valuable microorganisms that are beneficial to humans in various manners such as: