Final answer:
When a company pays cash to purchase supplies, the expense increases.
Step-by-step explanation:
When a company pays cash to purchase supplies, two accounts are affected: the Cash account and the Supplies account.
The Cash account is an asset account, and when cash is paid, the Cash account decreases because the company is using cash to make the purchase.
The Supplies account is an expense account, and when supplies are purchased, the Supplies account increases because the company is incurring an expense.
Therefore, the correct answer is:
b. expense increases