Covalent modification:. a. can involve the addition of phosphate groups.
b. can activate an enzyme.
c. produces modifications that can sometimes be reversed.
d. affects the activity of an enzyme by adding or removing a chemical group.
e. all of these are correct.

Option E.

All is correct.

Explanation:

A. can involve the addition of phosphate groups.

b. can activate an enzyme.

c. produces modifications that can sometimes be reversed.

d. affects the activity of an enzyme by adding or removing a chemical group.

Because Covalent modifications are enzymes catalyzed changes in the production of protein that involve the removal or addition chemical groups.

Covalent modifications can target a single or many Amino acids and it will alter their chemical properties.

Addition of phosphate group is a covalent modification because it control enzymes activity.

Covalent modification is reversible because it involves addition or removal of phosphoryl group to enzymes.

covalent attachment of another molecule can affect the activity of enzymes and many other proteins. In these occurence, the molecule that act as donor provides a functional moiety that modifies the properties of the enzyme.

d. the weight of the book