Missing diagram makes configuration ambiguous

Steps:

• Without the diagram, the exact placement of r relative to the parallel resistors is unclear.
• Standard assumption leads to r = (E - 2)/1.6, where V = 0.8 × 2.5 = 2 V and total current = 1.6 A.
• This does not match any choice, which are simple E divided by a constant.
• Diagram likely shows non-standard setup (e.g., r in one branch), but details absent.

Why C is correct:

• Not enough information.

Why the others are wrong:

• A: Not enough information.
• B: Not enough information.
• D: Not enough information.

Final answer: Not enough information.