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.