Final answer:
The correct completion for the sentence is 'c. Invest in, fairly', as transactional suppliers do not expect significant investment in understanding their capabilities, but do expect fair treatment. In business, it is beneficial to think and act reasonably and less emotionally with all suppliers.
Step-by-step explanation:
Transactional suppliers understand that they are not the most important accounts in the eyes of their clients, and they usually don't expect their clients to heavily invest in understanding or appreciating their capabilities. The correct completion for the sentence, 'Transactional suppliers know they are not your most important accounts. They don't expect you to __________ their capabilities. But, they do expect you to treat them __________.' is 'c. Invest in, fairly.' While deeper relationships might be built with strategic suppliers, transactional suppliers still expect a basic level of professional treatment which is fair and respects the terms of the agreement between them and the client.
It is important in business to think and act reasonably and less emotionally when dealing with suppliers, whether they are transactional or strategic. A fair and respectful relationship can lead to business sustainability and efficiency where both parties stand to benefit. This approach is also advantageous for individuals, as they might earn money and achieve their goals more effectively through rational thinking and planning, rather than reacting impulsively or irrationally to situations.