You and a friend are being chased by a bear. under these conditions levels of epinephrine are increased due to metabolism of which of the following amino acids

For producing epinephrine , tyrosine is required .

Explanation:

Epinephrine is produced  in  adrenal medulla, where the amino acid tyrosine is transformed to norepinephrine. An enzyme known as phenylethanolamine N-methyltransferase catalyzes the methylation of norepinephrine to epinephrine.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

the answer is option a.