Following tetrapeptide can be represented as

(F, L, D, Y, I, Q, P are one letter codes for amino acids)

Explanation

Peptide sequences are read from the $$N$$-terminus to the $$C$$-terminus.

The $$N$$-terminus contains the free amino group $$H_2N-$$, while the $$C$$-terminus contains the free carboxyl group $$-COOH$$.

The first amino acid has the side chain:

$$-CH_2C_6H_5$$

This is the side chain of phenylalanine.

Its one-letter code is:

$$F$$

It cannot be proline because proline contains a cyclic secondary amine, whereas the given structure has a free primary amino group.

The second amino acid has the side chain:

$$-CH_2CH(CH_3)_2$$

This is the side chain of leucine.

Its one-letter code is:

$$L$$

The third amino acid has the side chain:

$$-CH_2COOH$$

This is the side chain of aspartic acid.

Its one-letter code is:

$$D$$

The fourth amino acid has the side chain:

$$-CH_2C_6H_4OH$$

This is the side chain of tyrosine.

Its one-letter code is:

$$Y$$

Therefore, the peptide sequence is

$$F-L-D-Y$$

Hence, the correct answer is Option B.