What Is Meant by Vertical Offset

What is meant by vertical offset?

A) The deduction of capital charges because long and short positions in the same maturity bucket but in different instruments more than offset each other.
B) The assignment of additional capital charges because long and short positions in the same maturity bucket but in different instruments cannot perfectly offset each other.
C) The deduction of capital charges because long and short positions in different maturity buckets but in the same instrument more than offset each other.
D) The assignment of additional capital charges because long and short positions in different maturity buckets but in the same instrument cannot perfectly offset each other.