$A$ sequence of how many nucleotides in messenger $RNA$ makes a codon for an amino acid?

$A$ light pointer fixed to one prong of a tuning fork touches a vertical plate. The fork is set vibrating and the plate is allowed to fall freely. If eight oscillations are counted when the plate falls through $10 \, cm$,the frequency of the tuning fork is .... $Hz$

$A$ transformer is used to light a $140 \, W, 24 \, V$ lamp from a $240 \, V \, AC$ mains. The current in the main cable is $0.7 \, A$. The efficiency of the transformer is......$\%$

$A$ particle of mass $4 M$ which is initially at rest explodes into three pieces of masses $M$,$M$ and $2 M$. The equal masses move along $X$ and $Y$-axes with velocities $4 ~ms^{-1}$ and $6 ~ms^{-1}$,respectively. The magnitude of the velocity of the heavier mass is

White vitriol is:

Which of the following is not a synthetic polymer?