Choose the correct statement. A) All proteins have 20 amino acids. B) Proteins are formed by peptide bonds. C) Both ends of a protein are similar. D) All proteins are soluble.

Correct option is B. Proteins are formed by peptide bonds. Proteins are polypeptides, that is they are made of multiple amino acids linked together by peptide bonds. So, the correct answer is 'Proteins are formed by peptide bonds'.