From I and II:
There are two shelves in between the ones of M and G.
| Case 1 | Case 2 | Case 3 | Case 4 | 
| M/G |  |  |  | 
|  | M/G |  |  | 
|  |  | M/G |  | 
| G/M |  |  | M/G | 
|  | G/M |  |  | 
|  |  | G/M |  | 
|  |  |  | G/M | 
N has his shelf immediately above A. D has his shelf immediately above N. So, cases 2 and 3 are invalid.
| Case 1 | Case 4 | 
| M/G | D | 
|  | N | 
|  | A | 
| G/M | M/G | 
| D |  | 
| N |  | 
| A | G/M | 
E has his shelf above G but not immediately.
There are two shelves in between the ones that belong to T and A. So, case 1 is invalid.
So, E has kept his things immediately below M. Hence, statements I and II together are sufficient.
From II and III:
There are two shelves in between the ones of M and G.
| Case 1 | Case 2 | Case 3 | Case 4 | 
| M/G |  |  |  | 
|  | M/G |  |  | 
|  |  | M/G |  | 
| G/M |  |  | M/G | 
|  | G/M |  |  | 
|  |  | G/M |  | 
|  |  |  | G/M | 
E has his shelf above T. E has his shelf below A but not immediately. There are two shelves in between the ones that belong to T and A.
| Case 1 | Case 2(i) | Case 2(ii) | Case 3 | Case 4 | 
| M/G | A |  |  |  | 
|  | M/G | M/G | A |  | 
| A | E |  | M/G | A | 
| G/M | T | A | E | M/G | 
| E | G/M | G/M | T | E | 
| T |  | E | G/M | T | 
|  |  | T |  | G/M | 
D has his shelf immediately above N. There is one shelf in between M and N. So, cases 1, 2(ii), 3 are invalid.
| Case 2(i) | Case 4 | 
| A | D | 
| G | N | 
| E | A | 
| T | M | 
| M | E | 
| D | T | 
| N | G | 
G has his shelf below T and not adjacent to that of D. So, case 2(i) is invalid.
E has kept his things immediately below M. Hence, statements II and III together are sufficient.
From I and III:
There are two shelves in between the ones that belong to T and A.
| Case 1 | Case 2 | Case 3 | Case 4 | 
| T/A |  |  |  | 
|  | T/A |  |  | 
|  |  | T/A |  | 
| A/T |  |  | T/A | 
|  | A/T |  |  | 
|  |  | A/T |  | 
|  |  |  | A/T | 
E has his shelf above G but not immediately. E has his shelf below A but not immediately. So, A must be above T. So, case 4 is invalid. N has his shelf immediately above A. So, case 1 is invalid. There is one shelf in between the ones of A and D.
There is one shelf in between M and N.
| Case 2 | Case 3 | 
| N | D/ | 
| A | N | 
| M | A | 
| D | M | 
| T | /D | 
|  | T | 
|  |  | 
E has his shelf above G but not immediately. E has his shelf below A but not immediately. So, case 2 is invalid.
So, E has kept his things immediately below M. So, statements I and III are sufficient together.
Hence, any two of the three statements together are sufficient.