Which of the following is the correct increasing order of ionic character?

Which of the following is not correct?

Seven white balls and three black balls are randomly arranged in a row. The probability that no two black balls are placed adjacently is

The coil in a moving coil galvanometer experiences a torque proportional to the current passing through it. If a steady current $i$ is passed through it,the steady deflection of the coil is found to be $90^o$. Now,the steady current is switched off and a charge $q$ is suddenly passed through the coil. If the coil has $N$ turns of area $A$ and its moment of inertia is $I$ about the axis of rotation,then the maximum angle through which it deflects upon passing charge $q$ is:

The equation of the parabola with focus $(0, 0)$ and directrix $x + y = 4$ is

Select the correct statement.