Which of the following is an amphoteric hydroxide?

The angle between the lines whose direction cosines satisfy the equations $l + m + n = 0$ and $l^2 = m^2 + n^2$ is

The approximate atomic weight of an element is $26.89$. If its equivalent weight is $8.9$,the exact atomic weight of the element would be:

The dependence of disturbances due to two waves on time is shown in the figure. The ratio of their intensities $I_1 / I_2$ will be

Which of the following animals has a myogenic heart?

$A$ conductor of resistance $3 \Omega$ is stretched uniformly until its length is doubled. The wire is now bent in the form of an equilateral triangle. The effective resistance between the ends of any side of the triangle in ohms is