'A' is longer than 'B' but shorter than 'C'. 'D' is not the shortest among all. Who is tallest among all.

Cannot determined

ATQ,

A is longer than B, but shorter than C and D is not shortest among all.

On the basis of above information, it is not clear that who is the tallest among them.

Possibility is that C is the tallest, followed by D, A and B in that order. Alternatively, D could be taller than C, with A and B being shorter.

Therefore option D is correct.