why the answers of b and c are incorrect?

need some explanations.

Financial Accounting with Connect Plus |(8th Edition) 5 Chapter 5, Problem 84MCQ O D 1 Bookmark Show all steps: ON E Problem Which of the following transactions results in a decrease in the return on assets ratio? A. Increasing the sales price of the products sold. B. An increase in the net profit margin ratio. C. Purchasing land by signing a long-term note payable. D. Collecting cash from an account receivable. Step-by-step solution Step 1 of 1 ^ A. Increasing the sales price of the products sold. B. An increase in the net profit margin ratio. C. Purchasing land by signing a long-term note payable. D. Collecting cash from an account receivable. Return on assets is net income divided by average total assets. Total assets increase by land