The first diagram is of the reverse bias of diode.
The 2nd diagram is simple ohm’s law but having a turn on voltage 0.7 volts.
Also slop =1000Ω.
That means a diode in a series connection with a 1kΩ resistance.
Furthermore, the 3rd and 4th diagram represents a diode in reverse and forward bias.
The last two diagrams shows a turn on potential of 1.4v. This is quite certain for having two 0.7v batteries in series or in other words both the diode is in same orientation.
The final structure will be as shown.
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