Correct option is C
The correct substitution of the highlighted segment is “full of grief.”
Error identification: The phrase "full of grieve" is incorrect because "grieve" is a verb, not a noun. The correct word is "grief," which is a noun.
Grammatical Rule used: The noun form "grief" is used to describe a state of deep sorrow, while "grieve" is the verb form.
Corrected sentence: The heart that is full of grief is heavy.