Which is the most important cereal crop of temperate regions?

Which of the following is a bidentate ligand?

The metal used for the de-bromination reaction of $1, 2-dibromoethane$ is:

Two thick wires and two thin wires,all of the same material and same length,form a square in three different ways $P$,$Q$,and $R$ as shown in the figure. With the current connection shown,the magnetic field at the centre of the square is zero in which cases?

$A$ charge $Q$ is enclosed by a Gaussian spherical surface of radius $R$. If the radius is doubled,then the outward electric flux will

In the figure below, what is the potential difference between the points $A$ and $B$ and between $B$ and $C$ respectively in steady state?