What does a bank's duration gap measure?

a. The duration of short-term buckets minus the duration of long-term buckets.
b. The duration of the bank's assets minus the duration of its liabilities.
c. The duration of all rate-sensitive assets minus the duration of rate-sensitive liabilities.
d. The duration of the bank's liabilities minus the duration of its assets.
e. The duration of all rate-sensitive liabilities minus the duration of rate-sensitive assets.

b