Change of $\mathrm{pH}$ may disturb protein structure and thus affecting its functions. Which level of protein structure is not generally affected by the change in $\mathrm{pH}$ ?

The correct sequence of amino acids present in the tripeptide given below is:

Given below are two statements:

Statement I: A protein is imagined as a line, the left end represented by first amino acid (C-terminal) and the right end represented by last amino acid (N-terminal).

Statement II: Adult human haemoglobin, consists of 4 subunits (two subunits of $\alpha$ type and two subunits of $\beta$ type).

In the light of the above statements, choose the correct answer from the options given below: