Answer:
Option A
Explanation:
We have 3 patterns :
I. ABCD .....XYZ, which occurs only once.
II. YX ..... BA, which repeats alternately.
III. BC .....YZ, which repeats alternately.
Now, I has 26 terms. So, number of terms before the desired term = (999 - 26) =973.
Each of the patterns which occur after I, has 25 letters.
Now, 973 ÷ 25 gives quotient = 38 and remainder = 23.
Thus, the 1000th term of the given series is the 24th term of the 39th pattern after I.
Clearly, the 39th pattern is II and its 24th term is B.