Based on the answer (Choice B), is it correct to say that, under US GAAP, the stockholders’ equity of the parent (i.e, investor) company under the equity method (i.e., “one-line” consolidation) of accounting will be same as that under the purchase method of accounting?
Yes. The Equity method asset = consolidation asset - consolidation liability. Basically you raise both assets and liabilities for consolidation purpose but the S/E would be the same. Simarly result would be true for I/S as well, you will have both revenue and expense increase under consolidation but the NI would be the same.