Which of the following amino acids has the lowest iso-electric point $(pI)$?

The naturally occurring amino acid that contains only one basic functional group in its chemical structure is

Read the following statements carefully:
$(A)$ Albumin is a simple protein.
$(B)$ The amino acid alanine contains an acidic side chain.
$(C)$ Insulin is a hormone.
$(D)$ Muscles contain the protein keratin.
Point out the wrong statements in the above set of statements.

The artificial sweetener aspartame $(A)$,$H_3N^{+}-CH(CH_2COO^{-})-CONH-CH(CH_2Ph)-COOCH_3$,is converted to . . . . . . on storage for extended periods of time in aqueous solution:

The number of tripeptides formed by $3$ different amino acids using each amino acid once is.................

Which one of the nitrogen atoms of histidine is protonated first?