Consider a box with three terminals on top of it as shown in figure.

Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement
A student performs an experiment in which any two of these three terminals are connected in the circuit shown in figure.
The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit. The graphs are
(i) When A is positive and B is negative

(ii) When A is negative and B is positive

(iii) When B is negative and C is positve

(iv) When B is positive and C is neagtive

(v) When A is positive and C is negative

(vi) When A is negative and C is positive

From these graphs of current `-` voltage characteristic shown in fig. (c) to (h) determine the arrangement of components between A, B and C.

Explanation

In V-I graph of condition (i), a reverse characteristics is shown in Fig. Here A is connected to n-side of p-n junction I and B is connected to p-side of p-n junction I with a resistance in series.
In V-I graph of condition (ii), a forward characteristic is shown in Fig. , where 0.7 V is the knee voltage of p-n junction and `1//"slope"=(1//1000)Omega`.
It means A is connected to n-side of p-n junction I and B is connected to p-side of p-n junction I and resistance R is in series of p-n junction I between A and B.
In V-I graph of condition (iii), a forward characteristics is shown in Fig., where 0.7 V is the knee voltage. In this case p-side of p-n junction-II is connected to C and n-side of p-n junction II to B.
In V-I graph of condition (iv), (v) and (vi) also concludes the above connecttions of p-n junction I and II along with a resistance R. Thus, the arrangement of p-n I, p-n II and resistance R between A, B and C will be as shown in Fig .