Which of These Sentences Shows Parallel Structure

Multiple Choice

Which of these sentences shows parallel structure?

A) The line cook should follow the printed recipe; do not change the chef's dessert.
B) Our current structure is saving us money and reducing our downtime.
C) The speakers will include partners of accounting firms, businesspeople, and insurance agents.
D) We need to buy more drywall, lumber, tools, and hire the subcontractors.