Question

The building blocks of proteins are _____. nucleic acids amino acids sugars fats

Answer 1

Answer: Amino acids are the building blocks of proteins.

There are 20 standard amino acids which make up the human and other mammalian proteins. In a protein molecule, amino acids are held together by peptide bond which is formed between -COOH (carboxylic group) of one amino acid and $NH_2$ (amino group) of another amino acid.

They can be broadly divided as-

1) Charged amino acids

• Lysine (K)

• Arginine (R)
• Aspartic acid (D)
• Glutamic acid (E)  

2) Hydrophobic amino acids

• Glycine (G)
• Alanine (A)
• Proline (P)
• Leucine (L)
• Isoleucine (I)
• Methionine (M)
• Phenylalanine (F)
• Valine (V)

3) Polar amino acids

• Glutamine (Q)
• Histidine (H)
• Asparagine (N)
• Serine (S)
• Threonine (T)
• Cysteine (C)
• Tyrosine (Y)
• Tryptophan (W)

Answer 2

The building blocks of proteins are "Amino acids"

So, option B is your answer.

Hope this helps!