Complete the square with the letters of TRUCK so that no row, column or diagonal line contains the same letter more than once. What letter must replace the question mark?

T R U C K	T R U C K	T R U C K	T	T R U C K
? T R U C K	T R U C K	T R U C K	T R U C K	T R U C K
T R U C K	T R U C K	T R U C K	R	T R U C K
T R U C K	U	T R U C K	K	T R U C K
T R U C K	T R U C K	T R U C K	T R U C K	C

 

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