From the main question stem we know -
D is the average of A and E. So if we imagine a number line, D lies in between A and E.
Note, A and E can be on either side of D (as we do not know which out of the two is greater, A or E). So there can be two possible arrangements as shown below -]
Option 1 ) -------A-------D-------E-------
Option 2 ) -------E-------D-------A-------
Statement 11) A - E < 0
A < E
2) B is not the smallest
As A is less than E, it lies to the right of the number line. Hence out of the two options presented above, only Option 1 is in consideration.
From the second point we know that B is not the smallest, therefore B lies to the right of A at any position.
With this constraint in mind out of many possible arrangements, two possibilities are -
-------A-------D-------E-------B
-------A-------D-------E-------C
Hence we see that either B or C can be the largest.
Hence the statement in itself is
not sufficient.
Statement 21) E - C is negative
E - C < 0
E < C
2) B is not the largest
From the first statement we can conclude that E lies to the left of C in a number line.
Also its given that B is not the largest, which means it is not the right most element.
Again, if we look at the possibilities, E and A can be at the right most position.
-------A-------D-------E-------C-------
-------E-------C-------D-------A-------
The other information given is B is not the largest. However, out of the above two possibilities presented, both are valid.
Hence the statement in itself is
not sufficient.
CombiningFrom statement 1 -
Only Option 1 can be considered
A lies to the left of E
From statement 2-
B is not the largest.
E should lie to the left of C
From the largest number perspective, the arrangement is as follows -
-------A-------D-------E-------C-------
Note : B can lie anywhere between A and C; however, the position is immaterial to what's asked in the question.
We can say for sure that C is the largest.
Hence combining the statements we have a definite answer.Hence C