Which of the following hormones is a derivative of an amino acid?

Which of the following would produce a buffer solution when mixed in equal volumes?

$A$ circular disc of radius $R$ is removed from a bigger circular disc of radius $2R$ such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance $\alpha R$ from the centre of the bigger disc. The value of $\alpha$ is

If a polygon of $n$ sides has $275$ diagonals,then $n$ is equal to

$A$ gaseous mixture contains $50\%$ helium and $50\%$ methane by volume. What is the percentage of methane by weight in the mixture?

Consider the following statements $A$ and $B$ and identify the correct answer.
$A$. In an elastic collision,if a body suffers a head-on collision with another of the same mass at rest,then the first body comes to rest while the other starts moving with the velocity of the first one.
$B$. Two bodies of equal mass suffering a head-on elastic collision merely exchange their velocities.