When Monaro met with one of his biggest customers, the customer expressed that they may be switching suppliers. To keep the customer, Monaro sets up a meeting to discuss the customer's needs. He then offers to tailor his product offering specific to the customer's needs. This is an example of $\_\_\_\_\_.$

a$.$ a transactional exchange

b$.$ relationship marketing

c$.$ an operational linkage

d$.$ a value$-$adding exchange