Choice "B" is correct. Under U.S. GAAS, when the group engagement partner assumes responsibility for the component auditor's work, the group engagement partner would not mention the component auditor in the audit report (opinion). The group engagement auditor would generally assume responsibility after reviewing the audit documentation of the component auditor and performing supplemental audit tests, or by reputation, e.g., if the component auditor is a correspondent (foreign) firm in which the group engagement partner auditor has developed confidence.
Choices "a" and "d" are incorrect. When the group engagement partner finds it impractical to review the component auditor's work, or when the FS audited by the other auditor are material, it is more likely that the group engagement partner will divide responsibility and make reference to the component auditor.
Choice "c" is incorrect. The group engagement partner should always make inquiries regarding the independence and professional reputation of the component auditor. Inability to become satisfied in this regard would constitute a scope limitation, resulting in a qualified opinion or disclaimer of opinion. In either of these scenarios, it is likely that the component auditor would be mentioned within an explanatory paragraph.