List the given amino acids

The amino acids given are:

$\text{Arginine, Phenylalanine, Aspartic acid, Cysteine, Histidine, Valine, Proline}$

Recall the essential amino acids

In standard JEE chemistry, the essential amino acids commonly listed are:

$\text{Valine, Leucine, Isoleucine, Lysine, Methionine, Threonine, Phenylalanine, Tryptophan}$

and often also:

$\text{Histidine, Arginine}$

especially in school/JEE-level classification where histidine and arginine are treated as essential or semi-essential.

Check each amino acid from the list

• Arginine $\rightarrow$ essential/semi-essential at JEE level
• Phenylalanine $\rightarrow$ essential
• Aspartic acid $\rightarrow$ non-essential
• Cysteine $\rightarrow$ non-essential
• Histidine $\rightarrow$ essential
• Valine $\rightarrow$ essential
• Proline $\rightarrow$ non-essential

Count the essential amino acids

Essential ones in the list are:

$\text{Arginine, Phenylalanine, Histidine, Valine}$

Total number:

$4$

Comparison with stored answer

Stored correct answer = $4$

This matches the derived answer.