By clause B a person who writes his congressman and threatens not to vote/donate in the next election cycle is a terrorist (threat/coercion).
If the key is intent, then a poet who writes an anti-government poem is a terrorist.
if a and (b1 or b2 or b3) and c
terrorist = true
endSo an attack designed to destroy an unoccupied building would not be terrorism under the structure you describe above.
The definition does not state that all of the clauses must be satisfied for something to qualify as terrorism, and as I showed above, satisfying a single clause is trivial (and clearly not terrorism).
Logic would dictate that the meaning of that is "if A and (B[1] or B[2] or B[3]) and C", but it's not explicitly there.