Which of the following $\alpha-$amino acids does not contain a chiral carbon?

Which of the following statements are correct? A) $\alpha - \text{amino acids present in protein is L- amino acid.}$ B) $\text{Amino acids contain } NH_2 \text{ as well as COOH group.}$ C) $\text{Number of amino group and carboxylic group are same in amino acids always.}$ D) $\text{Tryosine was firstly obtained from cheese.}$ Choose the correct alternatives from below:

Which of the following amino acids is optically inactive?

Which of the following is a Zwitter ion?

Which one of the following statements is true for protein synthesis (translation)?

What does the secondary structure of proteins represent?