Which one of the following pairs is not correctly matched?

$A$ particle is moving along a circular path with constant speed and centripetal acceleration $a$. If the speed is doubled,the ratio of its acceleration after and before the change is

If a convex lens of focal length $80 \ cm$ and a concave lens of focal length $50 \ cm$ are combined together,what will be their resulting power?

The correct order of dipole moment is

Consider the following statements $A$ and $B$. Identify the correct choice in the given answers.
$A$. The refractive index of the extra-ordinary ray depends on the angle of incidence in double refraction.
$B$. The vibrations of light waves acquire one-sidedness for both ordinary and extraordinary rays in double refraction.

$ACTH$ is secreted by