Which endangered animal is the source of the world's finest, lightest, warmest, and most expensive wool-the Shahtoosh?

In the given figure, the magnetic field at the centre will be:

Who first discovered lichens?

In which plant group is the structure shown below found?

$A$ cylinder of height $h$ is filled with water and is kept on a block of height $h / 2$. The level of water in the cylinder is kept constant. Four holes numbered $1, 2, 3$ and $4$ are at the side of the cylinder and at heights $0, h / 4, h / 2$ and $3h / 4$ respectively from the base of the cylinder. When all four holes are opened together,the hole from which water will reach the farthest distance on the plane $PQ$ is the hole number

Which microorganism is used for the commercial production of citric acid?