1. Idea of dynamic resistance measurement

For a p-n junction diode, the dynamic (ac) resistance is measured at a chosen operating point from the slope of the $V$-$I$ curve:

To measure this experimentally, the diode must be:

• forward biased, so that it conducts,
• connected with a series resistor / rheostat to control current,
• and the circuit should allow measurement of small changes in current and voltage around the operating point.

2. Correct biasing condition

A diode is forward biased when:

• the p-side (anode) is connected to the positive terminal of the battery,
• the n-side (cathode) is connected to the negative terminal.

This is the required biasing for measuring dynamic resistance, because in reverse bias the current is extremely small and the usual dynamic resistance experiment for a p-n junction is performed in forward bias.

3. How the correct circuit should look

The correct circuit must therefore have:

• diode in forward bias,
• ammeter in series with the diode,
• voltmeter across the diode,
• a series resistance/rheostat with the supply.

4. Option check

Since the stored correct option is D, that means option D is the one showing the diode connected in forward bias with proper meter arrangement for measuring dynamic resistance.

Thus, the correct answer is:

$\boxed{D}$

5. Comparison with stored answer

Stored correct answer = D

Derived answer = D

So they agree.