Which of the following proteins is insoluble in any solvent?

Which of the following statements are correct regarding amino acids?
$A$. They are substituted methanes.
$B$. Serine is an aromatic amino acid.
$C$. Valine is a neutral amino acid.
$D$. Lysine is an acidic amino acid.
Choose the correct answer from the options given below:

Which bond connects two amino acids?

The antibodies in our body are complex $ \dots $.

Haemoglobin is a

$A$: Tertiary structure of protein is absolutely necessary for many biological activities of proteins.
$R$: In protein,only right-handed helices are observed.